Filed Pursuant to Rule 424(b)(5)
Registration No. 333-219186

The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying base prospectus are not an offer to sell these securities and they are not soliciting any offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED JUNE 19, 2018

PRELIMINARY PROSPECTUS SUPPLEMENT

(To Prospectus Dated July 6, 2017)

$            

ONEOK, Inc.

$            % Notes due 2028

$            % Notes due 2048

The notes due 2028 will bear interest at the rate of     % per year and will mature on             , 2028. The notes due 2048 will bear interest at a rate of     % per year and will mature on             , 2048. We refer to the 2028 notes and the 2048 notes collectively as the “notes.” Interest on the notes is payable on              and              of each year, beginning on             ,             . We may redeem the 2028 notes and the 2048 notes, in whole or in part, at any time at the redemption prices described under “Description of the Notes—Optional Redemption.”

The notes will be senior unsecured obligations of ours and will rank equally in right of payment with all of our existing and future unsecured senior debt.

The notes will be fully and unconditionally guaranteed, jointly and severally, on a senior unsecured basis by certain of our subsidiaries. Each guarantee will rank equally in right of payment with all of such guarantor’s existing and future unsecured senior debt. The notes and the guarantees will be effectively junior to any secured indebtedness of ours or any guarantor to the extent of the value of the assets securing such indebtedness and structurally subordinated to all indebtedness and other obligations of our subsidiaries that do not guarantee the notes.

Investing in the notes involves risks. See “Risk Factors” beginning on page S-6 of this prospectus supplement and on page 7 of the accompanying base prospectus.

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying base prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The notes will not be listed on any national securities exchange. Currently, there is no public market for the notes. We expect that the notes will be ready for delivery in registered book-entry form only through the facilities of The Depository Trust Company for the accounts of its participants, including Clearstream Banking, societé anonyme, and Euroclear Bank S.A./N.V., as operator of the Euroclear System, against payment in New York, New York, on or about             , 2018.

Joint Book-Running Managers

The date of this prospectus supplement is             , 2018.

TABLE OF CONTENTS

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RISK FACTORS

An investment in the notes involves risks. You should carefully consider all of the information contained in this prospectus supplement, the accompanying base prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying base prospectus as provided under “Where You Can Find More Information,” including our Annual Report on Form 10-K for the year ended December 31, 2017 and the risk factors described under “Risk Factors” therein. This prospectus supplement, the accompanying base prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying base prospectus also contain forward-looking statements that involve risks and uncertainties. Please read “Cautionary Statement Regarding Forward-Looking Statements” in this prospectus supplement and in the accompanying base prospectus. Our actual results could differ materially from those anticipated in such forward- looking statements as a result of certain factors, including the risks described elsewhere in this prospectus supplement, the accompanying base prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying base prospectus. If any of these risks occur, our business, financial condition or results of operation could be adversely affected.

Risks Related to the Notes

Our indebtedness and guarantee obligations could impair our financial condition and our ability to fulfill our obligations, including our obligations under the notes.

As of March 31, 2018, prior to giving effect to this offering, we had total consolidated indebtedness of approximately $8.1 billion. See “Capitalization.”

Our indebtedness and guarantee obligations could have significant consequences to you. For example, they could:

If we are unable to meet our debt-service obligations, we could be forced to restructure or refinance our indebtedness, seek additional equity capital or sell assets. We may be unable to obtain financing or sell assets on satisfactory terms, or at all.

We are not prohibited under the indenture governing the notes from incurring additional indebtedness. Our incurrence of significant additional indebtedness could exacerbate the negative consequences mentioned above and could materially adversely affect our ability to repay the notes.

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We have a holding company structure in which our subsidiaries and affiliates conduct our operations and own our operating assets, causing us to be dependent upon their distributions to make payments on the notes.

As we are a holding company, our subsidiaries and affiliates conduct a substantial portion of our operations and own a substantial portion of our operating assets. As a result, our ability to make required payments on the notes depends on the performance of our subsidiaries and their ability to make distributions, dividends, loans or advances to us. The ability of our subsidiaries to make distributions, dividends, loans or advances to us may be restricted by, among other things, future credit facilities, applicable state partnership laws and other laws and regulations. If we are unable to obtain the funds necessary to pay the principal amount of the notes at maturity, we may be required to adopt one or more alternatives, such as a refinancing of the notes. We cannot assure you that we would be able to refinance the notes on acceptable terms or at all.

As a result of our holding company structure, the notes will be structurally subordinated to liabilities and indebtedness of our subsidiaries other than ONEOK Partners and the Intermediate Partnership, which guarantee the notes, and effectively subordinated to any of our and the guarantors’ secured indebtedness to the extent of the assets securing such indebtedness.

A substantial portion of our operating assets are in our subsidiaries or our affiliates. The notes are not guaranteed by our subsidiaries or other affiliates, other than ONEOK Partners and the Intermediate Partnership, and our subsidiaries and such affiliates are not prohibited under the indenture from incurring additional indebtedness. As a result, holders of the notes will be structurally subordinated to claims of third-party creditors, including holders of indebtedness, of these non-guarantor subsidiaries and such affiliates. Claims of those other creditors, including trade creditors, secured creditors, governmental authorities, and holders of indebtedness or guarantees issued by our non-guarantor subsidiaries, will generally have priority as to the assets of our non-guarantor subsidiaries over claims by the holders of the notes. As a result, rights of payment of holders of our indebtedness, including the holders of the notes, will be structurally subordinated to all those claims of creditors of our non-guarantor subsidiaries. Assuming we had completed this offering on March 31, 2018, after giving effect to the application of the net proceeds as described in “Use of Proceeds” in this prospectus supplement, the notes and the guarantees would have been structurally subordinated to approximately $34.7 million of outstanding indebtedness of our non-guarantor subsidiaries. In addition, if either of ONEOK Partners or the Intermediate Partnership is no longer our subsidiary or no longer has any capital markets debt securities outstanding or guarantees any capital markets debt securities issued by us or the other guarantor, in each case other than the notes, so long as no default or event of default under the indenture has occurred or is continuing, they will be released from their obligations under the indenture, and its guarantees will no longer be in effect.

In addition, holders of our and the guarantors’ secured indebtedness would have claims with respect to the assets constituting collateral for such indebtedness that are prior to your claims under the notes or the guarantees. We do not currently have any secured indebtedness, but may have secured indebtedness in the future. In the event of a default on such secured indebtedness or our bankruptcy, liquidation or reorganization, our assets would be available to satisfy obligations with respect to the indebtedness secured thereby before any payment could be made on the notes or the guarantees. While the indenture governing the notes places some limitations on our ability to create liens, there are significant exceptions to these limitations, including with respect to sale and leaseback transactions, which will allow us to secure some kinds of indebtedness without equally and ratably securing the notes. To the extent the value of the collateral is not sufficient to satisfy the secured indebtedness, the holders of that indebtedness would be entitled to share with the holders of the notes and the holders of other claims against us with respect to our other assets.

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CAPITALIZATION

The following table sets forth our cash and cash equivalents and capitalization as of March 31, 2018, on:

This table should be read in conjunction with our historical consolidated financial statements and the notes to those financial statements that are incorporated by reference into this prospectus supplement and the accompanying base prospectus. You should also read this table in conjunction with “Management’s Discussion and Analysis of Financial Condition and Results of Operation” in our Annual Report on Form 10-K for the year ended December 31, 2017 and our Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, each of which is incorporated by reference herein.

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DESCRIPTION OF THE NOTES

The following description is a summary of the material terms of our notes. The descriptions in this prospectus supplement and the accompanying base prospectus contain a description of certain terms of the notes and the indenture under which the notes will be issued but do not purport to be complete, and reference is hereby made to the indenture that is an exhibit to the registration statement of which this prospectus supplement and the accompanying base prospectus are a part and to the U.S. Trust Indenture Act of 1939, as amended. This summary supplements the description of debt securities in the accompanying base prospectus and, to the extent it is inconsistent, replaces the description in the accompanying base prospectus. We urge you to read the indenture because it, and not this description, defines your rights as a holder of the notes. The following description of the notes and the description of the debt securities contained in the accompanying base prospectus are not complete and are subject to, and are qualified in their entirety by reference to, all the provisions of the indenture. You may request a copy of the indenture from us as set forth under “Where You Can Find More Information” below. Whenever particular defined terms of the indenture are referred to, those defined terms are incorporated herein by reference. In this “Description of the Notes,” references to “we,” “us” and “our” refer to ONEOK, Inc. and not to any of its subsidiaries.

General

Each series of notes will be issued under a senior indenture (as amended and supplemented from time to time, including supplements setting forth the terms of the notes) between us, ONEOK Partners, the Intermediate Partnership and U.S. Bank National Association, as trustee (the indenture, as supplemented, is referred to as the “indenture”).

The notes will be senior debt securities that will be our direct, unsecured obligations and will rank equally with all of our existing and future unsecured senior indebtedness. The notes will be guaranteed by ONEOK Partners and Intermediate Partnership, two of our subsidiaries, however, such guarantors will not otherwise be subject to the covenants, obligations and duties provided for in the indenture solely in their capacity as guarantors. Each guarantee will rank equally in right of payment with all of such guarantor’s existing and future unsecured senior debt. The notes will be effectively junior to any secured indebtedness of any guarantor to the extent of the value of the assets securing such indebtedness and structurally subordinated to all indebtedness and other obligations of our subsidiaries that do not guarantee the notes. Assuming we had completed this offering on March 31, 2018, after giving effect to the application of the net proceeds as described in “Use of Proceeds” in this prospectus supplement, the notes and the guarantees would have been structurally subordinated to approximately $34.7 million of outstanding indebtedness of our non-guarantor subsidiaries.

We will issue the 2028 notes in an initial aggregate principal amount equal to $            . We will issue the 2048 notes in an initial aggregate principal amount of $            .

We will issue the notes in minimum denominations of $2,000 and whole multiples of $1,000 in excess thereof.

Because we conduct a substantial portion of our operations through our subsidiaries, our ability to service our debt, including our obligations under the notes, and other obligations are largely dependent on the earnings of our subsidiaries and the payment of those earnings to us, in the form of distributions, dividends, loans or advances from our subsidiaries or the repayment of loans or advances from us by our subsidiaries. Any payment of distributions, dividends, loans or advances by our subsidiaries could be subject to statutory or contractual restrictions. Our non-guarantor subsidiaries and affiliates have no obligation to pay any amounts due on the notes. The notes will be structurally subordinated to all of the existing and future debt and other liabilities of our non-guarantor subsidiaries and will be effectively subordinated to all of our and the guarantors’ future secured debt to the extent of the value of the collateral securing such debt.

The notes will not be subject to a sinking fund provision.

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The notes are subject to defeasance at our option as provided in the indenture. Unless we redeem the 2028 notes prior to maturity, the entire principal amount of the 2028 notes will mature and become due and payable, together with any accrued and unpaid interest thereon, on             , 2028. Unless we redeem the 2048 notes prior to maturity, the entire principal amount of the 2048 notes will mature and become due and payable, together with any accrued and unpaid interest thereon, on             , 2048.

The indenture does not contain provisions that afford holders of the notes protection in the event we are involved in a highly leveraged transaction or other similar transaction that may adversely affect such holders. The indenture does not limit our ability to issue or incur other unsecured debt or issue preferred stock.

Interest

Interest on the 2028 notes will accrue at     % per annum from             , 2018 and interest on the 2048 notes will accrue at     % per annum from             , 2018. Interest on the notes will be payable in U.S. dollars semi-annually in arrears on              and              of each year (each, an “Interest Payment Date”), beginning on             ,              and at maturity or, if applicable, earlier redemption. Interest payable on an Interest Payment Date will be paid to the Person in whose name the note is registered at the close of business on              or             , as the case may be (whether or not a business day in the City of New York), immediately preceding such Interest Payment Date. Interest payable at maturity or earlier redemption will be paid against presentation and surrender of the related notes. Interest on the notes will be computed on the basis of a 360-day year consisting of twelve 30-day months.

If any Interest Payment Date, the maturity date or any redemption date is not a business day in New York, New York, the required payment shall be made on the next succeeding day that is a business day as if it were made on the date such payment was due and no interest shall accrue on the amount so payable for the period from and after such Interest Payment Date, maturity date or redemption date, as the case may be, to such next business day.

Optional Redemption

On or after             , 2028 (    months prior to their maturity date), we may redeem the 2028 notes, in whole or in part, at any time and from time to time, on at least 30 days, but not more than 60 days, prior notice mailed to each holder of the 2028 notes to be redeemed, at a redemption price equal to 100% of the principal amount of the 2028 notes being redeemed plus accrued and unpaid interest to the redemption date. On or after             , 2048 (    months prior to their maturity date), we may redeem the 2048 notes, in whole or in part, at any time and from time to time, on at least 30 days, but not more than 60 days, prior notice mailed to each holder of the 2048 notes to be redeemed, at a redemption price equal to 100% of the principal amount of the 2048 notes being redeemed plus accrued and unpaid interest to the redemption date.

Prior to             , 2028 (    months prior to their maturity date) in the case of the 2028 notes and prior to             , 2048 (    months prior to their maturity date) in the case of the 2048 notes, the notes of each series will be redeemable, in whole or in part, at any time and from time to time, at our option, at a redemption price equal to the greater of:

plus, in each case, accrued and unpaid interest on the notes to the redemption date.

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The quotation agent means the reference treasury dealer appointed by us to serve in that capacity. The term reference treasury dealer means Citigroup Global Markets Inc., Merrill Lynch, Pierce, Fenner & Smith Incorporated, Mizuho Securities USA LLC and Wells Fargo Securities, LLC and their respective successors. If, however, any of Citigroup Global Markets Inc., Merrill Lynch, Pierce, Fenner & Smith Incorporated, Mizuho Securities USA LLC or Wells Fargo Securities, LLC ceases to be a primary U.S. government securities dealer in the United States, we will substitute another primary treasury dealer.

The adjusted treasury rate means, for any redemption date, the rate per annum equal to the semi-annual equivalent yield to maturity of the comparable treasury issue, assuming a price of the comparable treasury issue (expressed as a percentage of its principal amount) equal to the comparable treasury price for that redemption date. The comparable treasury issue means the U.S. treasury security selected by the quotation agent as having a maturity comparable to the remaining term of such notes to be redeemed, assuming the notes matured on the Par Call Date, that would be used, at the time of a selection and in accordance with customary financial practice, in pricing new issues of corporate debt securities of comparable maturity to the remaining term of such notes assuming the notes matured on the Par Call Date. The Par Call Date means             , 2028, with respect to the 2028 notes, and             , 2048 with respect to the 2048 notes, the date that is              months and              months prior to the maturity date of the 2028 notes and the 2048 notes, respectively.

The comparable treasury price means, for any redemption date, the reference treasury dealer quotation for the redemption date.

A reference treasury dealer quotation means, with respect to any redemption date, the average, as determined by us, of the bid and asked prices for the comparable treasury issue (expressed, in each case, as a percentage of its principal amount) quoted on the third business day preceding the redemption date.

In case of a partial redemption, selection of the notes for redemption will be made by such method as the trustee deems appropriate and fair and may provide for the selection for redemption of portions of the principal of notes. While the notes are held pursuant to the book-entry system, selection of notes for partial redemption will be made by the depositary pursuant to its practices and procedures. Notice of any redemption will be mailed by first class mail at least 30 days but not more than 60 days before the redemption date to each holder of the notes to be redeemed at its registered address. If any note is to be redeemed in part only, the notice of redemption that relates to the note will state the portion of the principal amount of the note to be redeemed. A new note in a principal amount equal to the unredeemed portion of the note will be issued in the name of the holder of the note upon surrender for cancellation of the original note. Unless we default in payment of the redemption price, on and after the redemption date, interest will cease to accrue on the notes or the portions of the notes called for redemption.

Mandatory Redemption

We will not be required to make any mandatory sinking fund payments with regard to the notes or to redeem any of the notes before maturity.

Covenants

The notes will have the benefit of the covenants set forth under “Description of Debt Securities—Certain Restrictive Covenants Under Our Senior Indenture” and “Description of Debt Securities—Consolidation, Merger and Sale of Assets” in the accompanying base prospectus.

Guarantees

ONEOK Partners and the Intermediate Partnership will unconditionally guarantee the payment of the notes on a senior unsecured basis, however, will not otherwise be subject to the covenants, obligations and duties provided for in the indenture solely in their capacity as guarantors. Notwithstanding the preceding sentence, ONEOK Partners and/or the Intermediate Partnership will be released from their obligations under the indenture,

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U.S. FEDERAL TAX CONSIDERATIONS

The following summary describes the material U.S. federal income tax consequences and, in the case of a non-U.S. holder (as defined below), the material U.S. federal estate tax consequences, of purchasing, owning and disposing of the notes. This summary applies to you only if you are a beneficial owner of notes and you acquire the notes in this offering for cash at a price equal to the issue price of that series of notes. The issue price of a series of notes is the first price at which a substantial amount of the notes of that series are sold for money to investors (other than to bond houses, brokers, or similar persons or organizations acting in the capacity of underwriters, placement agents or wholesalers).

This summary deals only with notes held as capital assets (generally, investment property) and does not deal with special tax situations such as:

If you are a partnership (or an entity or arrangement classified as a partnership for U.S. federal income tax purposes) holding notes or a partner in such a partnership, the U.S. federal income tax treatment of a partner in the partnership generally will depend on the status of the partner, the activities of the partnership and certain determinations made at the partner level, and you should consult your own tax advisor regarding the U.S. federal income and estate tax consequences of purchasing, owning and disposing of the notes.

This summary does not discuss all of the aspects of U.S. federal income and estate taxation that may be relevant to you in light of your particular investment or other circumstances. In addition, this summary does not discuss any U.S. state or local, or non-U.S., income tax consequences, any tax consequences under the Medicare tax on certain investment income or other tax consequences. This summary is based on U.S. federal income and estate tax law, including the provisions of the Internal Revenue Code, Treasury regulations, administrative rulings and judicial authority, all as in effect or in existence as of the date of this prospectus supplement. Subsequent developments in U.S. federal income and estate tax law, including changes in law or differing interpretations, which may be applied retroactively, could have a material effect on the U.S. federal income and

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estate tax consequences of purchasing, owning and disposing of notes as set forth in this summary. We cannot assure you that the Internal Revenue Service (the “IRS”) will not challenge one or more of the tax consequences described in this summary, and we have not obtained, nor do we intend to obtain, any ruling from the IRS with respect to the tax consequences of the purchase, ownership or disposition of the notes. Before you purchase notes, you should consult your own tax advisor regarding the particular U.S. federal, state and local and non-U.S. income and other tax consequences of acquiring, owning and disposing of the notes that may be applicable to you.

U.S. Holders

The following summary applies to you only if you are a U.S. holder (as defined below).

Definition of a U.S. Holder

A “U.S. holder” is a beneficial owner of a note or notes that is, for U.S. federal income tax purposes:

Payments of Interest

Interest on your notes will be taxed as ordinary interest income. In addition:

Sale or Other Disposition of Notes

Upon the sale, redemption, retirement, exchange or other taxable disposition (each, a “disposition”) of the notes, you generally will recognize taxable gain or loss equal to the difference, if any, between:

Your tax basis in your notes generally will be their cost. Your gain or loss generally will be capital gain or loss. This capital gain or loss will be long-term capital gain or loss if at the time of the disposition you have held the notes for more than one year. Subject to limited exceptions, your capital losses cannot be used to offset your ordinary income. If you are a non-corporate U.S. holder (including an individual), under current law, your long- term capital gain generally is subject to a preferential rate of U.S. federal income tax.

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UNDERWRITING

We are offering the notes described in this prospectus supplement through the underwriters named below. Citigroup Global Markets Inc., Merrill Lynch, Pierce, Fenner & Smith Incorporated, Mizuho Securities USA LLC and Wells Fargo Securities, LLC are the joint book-running managers of this offering and are acting as the representatives of the underwriters. We have entered into an underwriting agreement with the representatives on behalf of the underwriters. Subject to the terms and conditions of the underwriting agreement, each of the underwriters has severally agreed to purchase the principal amount of notes listed next to its name in the following table:

The underwriting agreement provides that the obligation of the several underwriters to pay for and accept delivery of the notes is subject to, among other things, the approval of certain legal matters by their counsel and certain other conditions. The underwriters are committed to take and pay for all of the notes being offered, if any are taken.

Each series of notes is a new issue of securities with no established trading market. We do not intend to apply for listing of the notes on any securities exchange or for quotation of the notes on any automated dealer quotation system. We have been advised by the underwriters that the underwriters intend to make a market for each series of the notes but are not obligated to do so and may discontinue market making at any time without notice. No assurance can be given as to the liquidity of the trading market for the notes.

Commissions and Discounts

The underwriters have advised us that they propose initially to offer the notes to the public at the public offering price on the cover page of this prospectus supplement and to dealers at that price less a concession not in excess of     % of the principal amount of the 2028 notes and     % of the principal amount of the 2048 notes. The underwriters may allow, and the dealers may reallow, to other dealers a discount not in excess of     % of the principal amount of the 2028 notes and     % of the principal amount of the 2048 notes to certain dealers. After the initial public offering, the public offering price and other selling terms may be changed.

The expenses of the offering, not including the underwriting discounts, are estimated at $             and are payable by us.

Price Stabilization, Short Positions

In order to facilitate the offering of the notes, the underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the notes. Specifically, the underwriters may overallot in connection with the offering, creating a short position in the notes for their own account. In addition, to cover overallotments or to stabilize the price of the notes, the underwriters may purchase and sell notes in the open market. These transactions may include short sales, stabilizing transactions and purchases to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of notes than they are required to purchase in the offering. Stabilizing transactions consist of certain bids or purchases made for the purpose of preventing or retarding a decline in the market price of the notes while the offering is in progress.

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The underwriters also may impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representatives have repurchased notes sold by or for the account of such underwriter in stabilizing or short covering transactions.

These activities by the underwriters may stabilize, maintain or otherwise affect the market price of the notes. As a result, the price of the notes may be higher than the price that otherwise might exist in the open market. The underwriters are under no obligation to commence such activities. If these activities are commenced, they may be discontinued by the underwriters at any time. These transactions may be effected in the over-the-counter market or otherwise.

Indemnification

We have agreed to indemnify the several underwriters against certain liabilities, including liabilities under the 1933 Act.

Settlement Cycle

Delivery of the notes will be made against payment therefor on or about the date specified in the last paragraph of the cover page of this prospectus supplement, which will be the              business day following the date of pricing (such settlement being referred to as “T+     ”). Pursuant to Rule 15c6-1 under the Exchange Act, trades in the secondary market are generally required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade notes on the day of pricing or on the next             business days will be required, by virtue of the fact that the notes will initially settle in T+     , to specify an alternate settlement arrangement at the time of any such trade to prevent a failed settlement.

Notice to Prospective Investors in the European Economic Area

The notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the European Economic Area (“EEA”). For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”); or (ii) a customer within the meaning of Directive 2002/92/EC (as amended, the “Insurance Mediation Directive”), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in Directive 2003/71/EC (as amended, the “Prospectus Directive”). Consequently, no key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling the notes or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the notes or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPs Regulation. This prospectus supplement has been prepared on the basis that any offer of notes in any Member State of the EEA will be made pursuant to an exemption under the Prospectus Directive from the requirement to publish a prospectus for offers of notes. This prospectus supplement is not a prospectus for the purposes of the Prospectus Directive.

Notice to Prospective Investors in the United Kingdom

In addition, in the United Kingdom, this document is being distributed only to, and is directed only at, and any offer subsequently made may only be directed at persons who are “qualified investors” (as defined in the Prospectus Directive) (i) who have professional experience in matters relating to investments falling within Article 19 (5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the “Order”) and/or (ii) who are high net worth companies (or persons to whom it may otherwise be lawfully communicated) falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”). This document must not be acted on or relied on in the United Kingdom by persons who are not relevant persons. In the United Kingdom, any investment or investment activity to which this document relates is only available to, and will be engaged in with, relevant persons.

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Notice to Prospective Investors in Canada

The notes may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the notes must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement and the accompanying prospectus (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory.

The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Notice to Prospective Investors in France

Neither this prospectus supplement nor any other offering material relating to the notes described in this prospectus supplement has been submitted to the clearance procedures of the Autorité des Marchés Financiers or of the competent authority of another member state of the European Economic Area and notified to the Autorité des Marchés Financiers. The notes have not been offered or sold and will not be offered or sold, directly or indirectly, to the public in France. Neither this prospectus supplement nor any other offering material relating to the notes has been or will be:

Such offers, sales and distributions will be made in France only:

The notes may be resold directly or indirectly, only in compliance with articles L.411-1, L.411-2, L.412-1 and L.621-8 through L.621-8-3 of the French Code monétaire et financier.

Notice to Prospective Investors in Australia

No prospectus or other disclosure document (as defined in the Corporations Act 2001 (Cth) of Australia (the “Corporations Act”)) in relation to the notes has been or will be lodged with the Australian Securities &

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Investments Commission (“ASIC”). This document has not been lodged with ASIC and is only directed to certain categories of exempt persons. Accordingly, if you receive this document in Australia:

Notice to Prospective Investors in Chile

The notes are not registered in the Securities Registry (Registro de Valores) or subject to the control of the Chilean Securities and Exchange Commission (Superintendencia de Valores y Seguros de Chile). This prospectus supplement and other offering materials relating to the offer of the notes do not constitute a public offer of, or an invitation to subscribe for or purchase, the notes in the Republic of Chile, other than to individually identified purchasers pursuant to a private offering within the meaning of Article 4 of the Chilean Securities Market Act (Ley de Mercado de Valores) (an offer that is not “addressed to the public at large or to a certain sector or specific group of the public”).

Notice to Prospective Investors in Hong Kong

The notes may not be offered or sold in Hong Kong by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong), or (ii) to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a “prospectus” within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong) and no advertisement, invitation or document relating to the notes may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to notes which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Notice to Prospective Investors in Switzerland

The notes may not be publicly offered in Switzerland and will not be listed on the SIX Swiss Exchange (“SIX”) or on any other stock exchange or regulated trading facility in Switzerland. This document has been prepared without regard to the disclosure standards for issuance prospectuses under art. 652a or art. 1156 of the Swiss Code of Obligations or the disclosure standards for listing prospectuses under art. 27 ff. of the SIX Listing Rules or the listing rules of any other stock exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the notes or the offering may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this document nor any other offering or marketing material relating to the offering, the Company, the notes have been or will be filed with or approved by any Swiss regulatory authority. In particular, this

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document will not be filed with, and the offer of the notes will not be supervised by, the Swiss Financial Market Supervisory Authority FINMA (“FINMA”), and the offer of the notes has not been and will not be authorized under the Swiss Federal Act on Collective Investment Schemes (“CISA”). The investor protection afforded to acquirers of interests in collective investment schemes under the CISA does not extend to acquirers of the notes.

Notice to Prospective Investors in Japan

The notes offered in this prospectus supplement have not been and will not be registered under the Financial Instruments and Exchange Law of Japan. The notes have not been offered or sold and will not be offered or sold, directly or indirectly, in Japan or to or for the account of any resident of Japan (including any corporation or other entity organized under the laws of Japan), except (i) pursuant to an exemption from the registration requirements of the Financial Instruments and Exchange Law and (ii) in compliance with any other applicable requirements of Japanese law.

Notice to Prospective Investors in Singapore

This prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the notes may not be circulated or distributed, nor may the notes be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA, in each case subject to compliance with conditions set forth in the SFA.

Where the notes are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

Underwriters’ Conflicts of Interest

The underwriters and their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, principal investment, hedging, financing and brokerage activities. The underwriters and their respective affiliates have provided in the past and may provide from time to time in the future certain commercial banking, financial advisory, investment banking and other services for us or our subsidiaries for which they will receive customary fees. Affiliates of certain of the underwriters are also agents and/or lenders under our credit facility.

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LEGAL MATTERS

Various legal matters, including the validity of the notes offered by this prospectus supplement, will be passed on for ONEOK by GableGotwals, Tulsa, Oklahoma and by Fried, Frank, Harris, Shriver & Jacobson LLP, New York, New York. The underwriters will be represented by Shearman & Sterling LLP, New York, New York.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control over Financial Reporting) incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2017 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Some of the statements contained in, or incorporated by reference into, this prospectus supplement and the accompanying base prospectus are forward-looking statements as defined under federal securities laws. The forward-looking statements relate to our anticipated financial performance (including projected operating income, net income, capital expenditures, cash flows and projected levels of dividends), liquidity, management’s plans and objectives for our future capital-growth projects and other future operations (including plans to construct additional natural gas and natural gas liquids pipelines and processing facilities and related cost estimates), our business prospects, the outcome of regulatory and legal proceedings, market conditions and other matters. We make these forward-looking statements in reliance on the safe harbor protections provided under federal securities legislation and other applicable laws. The following discussion is intended to identify important factors that could cause future outcomes to differ materially from those set forth in the forward-looking statements.

Forward-looking statements include the items identified in the preceding paragraph, the information concerning possible or assumed future results of our operations and other statements contained or incorporated by reference into this prospectus supplement or the accompanying base prospectus identified by words such as “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” “should,” “goal,” “forecast,” “guidance,” “could,” “may,” “continue,” “might,” “potential,” “scheduled” and other words and terms of similar meaning.

You should not place undue reliance on forward-looking statements. Known and unknown risks, uncertainties and other factors may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by forward-looking statements. Those factors may affect our operations, markets, products, services and prices. In addition to any assumptions and other factors referred to specifically in connection with the forward-looking statements, factors that could cause our actual results to differ materially from those contemplated in any forward-looking statement include, among others, the following:

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does not constitute part of this prospectus supplement or the accompanying base prospectus. All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by these factors. Any such forward-looking statement speaks only as of the date on which such statement is made, and other than as required under securities laws, we undertake no obligation to update publicly any forward-looking statement whether as a result of new information, subsequent events or change in circumstances, expectations or otherwise.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and other reports and other information with the SEC under the Exchange Act. You may read and copy any materials we file with the SEC at the SEC’s Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. You may obtain information on the operation of the Public Reference Room by calling the SEC at 1-800-732-0330. The SEC maintains a website (http://www.sec.gov) that contains reports, proxy and information statements and other information regarding issuers that file electronically with the SEC. Our SEC filings also are available on the SEC’s website. You also can obtain information about us at the offices of the NYSE, located at 11 Water Street, New York, New York 10005.

INCORPORATION BY REFERENCE

The SEC allows us to “incorporate by reference” information into this prospectus supplement. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus supplement, and information that we file later with the SEC will automatically update and supersede the previously filed information. We incorporate by reference the documents listed below and any future filings made by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, other than any portions of the respective filings that were furnished, pursuant to Item 2.02 or Item 7.01 of Current Reports on Form 8-K (including exhibits related thereto) or other applicable SEC rules, rather than filed, prior to the consummation of the offering under this prospectus supplement:

If information in incorporated documents conflicts with information in this prospectus supplement, you should rely on the most recent information. If information in an incorporated document conflicts with information in another incorporated document, you should rely on the most recent incorporated document.

Documents incorporated by reference are available from us without charge, excluding any exhibits to those documents unless the exhibit is specifically incorporated by reference as an exhibit in this document. You can obtain documents incorporated by reference in this document by requesting them in writing or by telephone at the following address and phone number:

ONEOK, Inc.

100 West Fifth Street

Tulsa, Oklahoma 74103

Attention: Corporate Secretary

Telephone: (918) 588-7000

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Debt Securities, Common Stock, Stock Purchase Contracts,

Stock Purchase Contract Units, Preferred Stock, Depositary Shares, and Warrants

Guarantee of Debt Securities of ONEOK, Inc. by ONEOK Partners, L.P. and by ONEOK Partners Intermediate Limited Partnership

We may offer and sell, from time to time in one or more issuances, (1) one or more series of debt securities, which may be senior or subordinated notes or debentures, or other senior or subordinated evidences of indebtedness, which may be fully and unconditionally guaranteed by ONEOK Partners, L.P. and by ONEOK Partners Intermediate Limited Partnership and which may include terms permitting or requiring holders to convert or exchange their debt securities for common stock, preferred stock or other securities, (2) shares of our common stock, (3) stock purchase contracts, (4) stock purchase contract units that consist of (a) a stock purchase contract and (b) senior or subordinated debt securities, or preferred stock, U.S. Treasury securities or other debt obligations of third parties, that may be used to secure the holders’ obligations under a purchase contract, (5) shares of our preferred stock, which may include terms permitting or requiring holders to convert or exchange their preferred stock for common stock or other securities, (6) depositary shares, or (7) warrants.

We will provide you with the specific terms of the particular securities being offered in supplements to this prospectus. Any prospectus supplement may also add, update, or change information contained in this prospectus. You should read this prospectus and each related prospectus supplement carefully before you make an investment decision. This prospectus may not be used to sell securities unless accompanied by a prospectus supplement.

Our common stock, par value $0.01 per share, is listed on the New York Stock Exchange under the symbol “OKE.”

Investing in these securities involves certain risks. Please read “Risk Factors” on page 7 of this prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this Prospectus is July 6, 2017.

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ABOUT THIS PROSPECTUS

The information contained in this prospectus is not complete and may be changed. We have not authorized anyone else to provide you with information other than the information provided in or incorporated by reference in this prospectus, any prospectus supplement, or documents to which we otherwise refer you. We are not making an offer of any securities in any jurisdiction where the offer is not permitted. You should not assume that the information in this prospectus, any prospectus supplement or any document incorporated by reference is accurate as of any date other than the date of the document in which such information is contained or such other date referred to in such document, regardless of the time of any sale or issuance of a security.

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission, or the SEC, utilizing a “shelf” registration process. Under this shelf registration process, we may sell different types of securities described in this prospectus in one or more offerings. This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering and the securities offered by us in that offering. The prospectus supplement may also add, update or change information in this prospectus. You should read both this prospectus and any prospectus supplement together with additional information described under the headings “Where You Can Find More Information” and “Incorporation by Reference.”

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by reference to the actual documents. Copies of some of the documents referred to herein have been filed or will be filed or incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you may obtain copies of those documents as described below in the section entitled “Where You Can Find More Information.”

Unless we otherwise indicate or unless the context requires, all references in this prospectus to:

WHERE YOU CAN FIND MORE INFORMATION

We have filed a registration statement on Form S-3 with the SEC under the Securities Act of 1933, as amended, or the Securities Act, that registers the securities offered by this prospectus. The registration statement, including the attached exhibits, contains additional relevant information about us. The rules and regulations of the SEC allow us to omit some information included in the registration statement from this prospectus.

We file annual, quarterly and current reports, proxy statements and other information with the SEC. You can read and copy any materials we file with the SEC at its Public Reference Room at 100 F Street, NE, Room 1580, Washington, D.C. 20549. You can obtain information about the operations of the SEC Public Reference Room by calling the SEC at 1-800-SEC-0330. The SEC also maintains a website that contains information we file electronically with the SEC, which you can access over the Internet at http://www.sec.gov. Our common stock is listed on the New York Stock Exchange (NYSE: OKE), and you can obtain information about us at the offices of the New York Stock Exchange, 11 Wall Street, New York, New York 10005. General information about us, including our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K,

and amendments to those reports, is available free of charge through our website at http://www.oneok.com as soon as reasonably practicable after we electronically file them with, or furnish them to, the SEC. Information on, or accessible through, our website is not incorporated into this prospectus or our other securities filings and is not a part of these filings.

INCORPORATION BY REFERENCE

The SEC allows us to “incorporate by reference” the information we have filed with the SEC. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC will automatically update and supersede the previously filed information.

The documents listed below and any future filings made by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, other than any portions of the respective filings that were furnished, pursuant to Item 2.02 or Item 7.01 of Current Reports on Form 8-K (including exhibits related thereto) or other applicable SEC rules, rather than filed, prior to the termination of the offerings under this prospectus are incorporated by reference in this prospectus:

You may request a copy of these filings (other than an exhibit to the filings unless we have specifically

incorporated that exhibit by reference into the filing), at no cost, by writing or telephoning us at the following address:

ONEOK, Inc.

100 West Fifth Street

Tulsa, Oklahoma 74103

Attention: Corporate Secretary

Telephone: (918) 588-7000

We have not authorized anyone to provide you with information other than the information contained or incorporated by reference in this prospectus or in any prospectus supplement. If anyone provides you with different or inconsistent information, you should not rely on it. We are not making an offer to sell, or soliciting an offer to buy, securities in any jurisdiction where the offer and sale is not permitted. You should assume that the information appearing or incorporated by reference in this prospectus, the applicable prospectus supplement or any applicable pricing supplement is accurate only as of the date of the documents containing the information, regardless of the time of its delivery or of any sale of our securities. Our business, financial condition, results of operations and prospects may have changed since those dates.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Some of the statements contained and incorporated in this prospectus are forward-looking statements as defined under federal securities laws. The forward-looking statements relate to our anticipated financial performance (including projected net income, capital expenditures, cash flow and projected levels of dividends), liquidity, management’s plans and objectives for our future growth projects and other future operations (including plans to construct additional natural gas and natural gas liquids facilities and related cost estimates), our business prospects, the outcome of regulatory and legal proceedings, market conditions and other matters. We make these forward-looking statements in reliance on the safe harbor protections provided under federal securities legislation and other applicable laws. The following discussion is intended to identify important factors that could cause future outcomes to differ materially from those set forth in the forward-looking statements.

Forward-looking statements include the items identified in the preceding paragraph, the information concerning possible or assumed future results of our operations and other statements contained or incorporated in this prospectus or the accompanying prospectus supplement identified by words such as “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” “should,” “goal,” “forecast,” “guidance,” “could,” “may,” “continue,” “might,” “potential,” “scheduled” and other words and terms of similar meaning.

You should not place undue reliance on the forward-looking statements. Known and unknown risks, uncertainties and other factors may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. Those factors may affect our operations, markets, products, services and prices. In addition to any assumptions and other factors referred to specifically in connection with the forward-looking statements, factors that could cause our actual results to differ materially from those contemplated in any forward-looking statement include, among others, the following:

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These factors are not necessarily all of the important factors that could cause actual results to differ materially from those expressed in our forward-looking statements. Other factors could also have material adverse effects on our future results. These and other risks are described in greater detail in Part 1, Item 1A, Risk Factors, in our Annual Report on Form 10-K for the year ended December 31, 2016, and Part II, Item 1A, Risk Factors, in our Quarterly Report on Form 10-Q for the period ended March 31, 2017 and in our other filings that we make with the SEC, which are available via the SEC’s website at www.sec.gov and our website at www.oneok.com. All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by these factors. Any such forward-looking statement speaks only as of the date on which such statement is made, and other than as required under securities laws, we undertake no obligation to update publicly any forward-looking statement whether as a result of new information, subsequent events or change in circumstances, expectations or otherwise.

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ABOUT ONEOK

We are a corporation incorporated under the laws of the state of Oklahoma, and our common stock is listed on the New York Stock Exchange under the trading symbol “OKE.” We apply our core capabilities of gathering, processing, fractionating, transporting, storing and marketing natural gas and NGLs through the rebundling of services across the value chains through vertical integration in an effort to provide our customers with premium services at lower costs. We are a leader in the gathering, processing, storage and transportation of natural gas in the United States. In addition, we own one of the nation’s premier natural gas liquids systems, connecting NGL supply in the Mid-Continent and Rocky Mountain regions and the Permian Basin with key market centers.

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RISK FACTORS

Before you invest in our securities, you should carefully consider the following risk factor with those risk factors included in our most recent Annual Report on Form 10-K, our Quarterly Reports on Form 10-Q and our other filings with the SEC that are incorporated herein by reference and any prospectus supplement or free writing prospectus used in connection with an offering of our securities, as well as the information relating to us identified above under “Cautionary Statement Regarding Forward-Looking Statements.”

If any of the risks discussed below or in the foregoing documents were actually to occur, our business, financial condition, results of operations, or cash flow could be materially adversely affected. In that case, our ability to pay dividends to our shareholders or pay interest on, or the principal of, any debt securities, may be reduced, the trading price of our securities could decline and you could lose all or part of your investment.

Our consolidated debt and guarantee obligations could make us more vulnerable to general adverse economic and industry conditions, limit our ability to borrow additional funds and place us at a competitive disadvantage.

In connection with our acquisition of the common units of ONEOK Partners, L.P. that we did not previously own, ONEOK Partners, L.P. and ONEOK Partners Intermediate Limited Partnership entered into agreements guaranteeing our obligations under our $2.5 billion revolving credit agreement and our outstanding senior notes and commercial paper, and we entered into agreements guaranteeing ONEOK Partners’ obligations under its $1.0 billion term loan agreement and its outstanding senior notes. We are therefore liable for these debt obligations of ONEOK Partners, L.P. in the event of a default. Our indebtedness, along with our guarantee obligations, could make us more vulnerable to general adverse economic and industry conditions, limit our ability to borrow additional funds, place us at competitive disadvantages compared with our competitors that have less debt and fewer guarantee obligations and/or have other adverse consequences.

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USE OF PROCEEDS

Unless we inform you otherwise in an applicable prospectus supplement, ONEOK will use the net proceeds from the sale of the offered securities for general corporate purposes. These purposes may include repayment and refinancing of debt, acquisitions, working capital, capital expenditures and repurchases and redemptions of securities. Pending any specific application, we may initially invest funds in marketable securities or apply them to the reduction of short-term indebtedness.

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RATIO OF EARNINGS TO FIXED CHARGES

Our ratio of earnings to fixed charges in each of the periods shown is as follows:

For purposes of computing the ratio of earnings to fixed charges, “earnings” consists of pretax income from continuing operations before adjustment for income or loss from equity investees plus fixed charges and distributed income of equity investees, less interest capitalized. “Fixed charges” consists of interest charges, the amortization of debt discounts and issue costs and the representative interest portion of operating leases.

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DESCRIPTION OF DEBT SECURITIES

The following description states the general terms and provisions of our debt securities. The debt securities offered by this prospectus will be issued under one of two separate indentures among us, ONEOK Partners, L.P. and ONEOK Partners Intermediate Limited Partnership (together with ONEOK Partners, L.P., the “Guarantors”), and U.S. Bank National Association, as trustee. We have filed the forms of indenture as exhibits to the registration statement of which this prospectus is a part. The debt securities will be unsecured obligations of ONEOK and will be either senior or subordinated debt. Senior debt will be issued under a senior indenture and subordinated debt will be issued under a subordinated indenture. The senior indenture and the subordinated indenture are sometimes referred to in this prospectus individually as an “Indenture” and collectively as the “Indentures.” Each prospectus supplement that we provide when we offer debt securities will describe the specific terms of the debt securities offered through that prospectus supplement and any general terms outlined in this section that will not apply to those debt securities. Unless otherwise specified in this prospectus, the term “debt securities” includes senior debt securities and subordinated debt securities and the descriptions of the debt securities describe both the senior debt securities and the subordinated debt securities unless otherwise specified in this prospectus or any prospectus supplement.

We have summarized the material terms and provisions of the Indentures in this section. The summary is not complete. We have filed the forms of each of the Indentures as exhibits to the registration statement of which this prospectus forms a part. You should read the applicable form of Indenture for additional information before you buy any debt securities. Each of the Indentures is qualified under the Trust Indenture Act. You should refer to the Trust Indenture Act for provisions that apply to the debt securities. This summary also is subject to and qualified by reference to the description of the particular terms of the debt securities described in the applicable prospectus supplement or supplements and pricing supplement or supplements. Capitalized terms used but not defined in this summary have the meanings specified in the applicable Indenture. In this section, “we,” “us” and “our” refer only to ONEOK, Inc. and not to any of our subsidiaries.

Debt securities issued under either Indenture will be issued as part of a series that will be established pursuant to a supplemental indenture or other authorized corporate action designating the specific terms of the series of debt securities. A prospectus supplement will describe these terms and will include, among other things, the following:

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We may sell the debt securities at a discount (which may be substantial) below their stated principal amount. These discounted debt securities may bear no interest or interest at a rate that at the time of issuance is below market rates. We will describe in the prospectus supplement any material United States federal income tax consequences and other special considerations.

Certain Restrictive Covenants Under Our Senior Indenture

Under the senior indenture, we have agreed to two principal restrictions on our activities for the benefit of holders of the senior debt securities. The restrictive covenants summarized below will apply to a series of senior debt securities (unless waived or amended) as long as any of those senior debt securities are outstanding or, unless the prospectus supplement for the series states otherwise. We have used in this summary description capitalized terms that we have defined below under “—Glossary.” Our Restricted Subsidiaries are those that own or lease a Principal Property.

Other than the restrictions on Liens and Sale/Leaseback transactions under the senior indenture described below, the Indentures and the debt securities do not contain any covenants or other provisions designed to protect holders of any debt securities in the event we participate in a highly leveraged transaction. The Indentures and the debt securities also do not contain provisions that give holders of the debt securities the right to require us to repurchase their securities in the event of change-in-control, recapitalization or similar restructuring or otherwise or upon a decline in our credit rating.

For these purposes, “debt” means obligations for money borrowed, evidenced by notes, bonds, debentures or other similar evidences of indebtedness.

Limitation on Liens

We agree that we will not, and will not permit any Restricted Subsidiary to, create, incur, issue or assume any debt secured by any Lien on any Principal Property, or on shares of stock or debt of any Restricted

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Subsidiary, without making effective provision for the outstanding securities issued under the senior indenture (except as otherwise specified pursuant to an applicable supplemental indenture) to be secured by the Lien equally and ratably with (or prior to) any and all debt and obligations secured or to be secured thereby for so long as such debt is so secured, except that the foregoing restriction will not apply to:

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Limitation on Sale/Leaseback Transactions

We agree that we will not, and will not permit any Restricted Subsidiary to, enter into any Sale and Leaseback Transaction unless:

Glossary

“Attributable Debt” means, as to any particular Sale and Leaseback Transaction under which any Person is at the time liable, at any date as of which the amount thereof is to be determined, the total net amount of rent required to be paid by that Person under the lease during the remaining term thereof (excluding amounts required to be paid on account of maintenance and repairs, services, insurance, taxes, assessments, water rates and similar charges and contingent rents), discounted from the respective due dates thereof at the weighted average of the rates of interest (or yield to maturity, in the case of senior debt securities originally sold at a discount) borne by the debt securities then outstanding under the senior indenture, compounded annually.

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“Consolidated Net Tangible Assets” means the total amount of assets (less applicable reserves and other properly deductible items) that under generally accepted accounting principles, or GAAP, would be included on a consolidated balance sheet of ours and our subsidiaries after deducting therefrom (A) all current liabilities, provided, however, that there will not be deducted billings recorded as revenues deferred pending the outcome of rate proceedings (less applicable income taxes thereon), if and to the extent the obligation to refund the same has not been finally determined, (B) appropriate allowance for minority interests in common stocks of subsidiaries and (C) all goodwill, trade names, trademarks, patents, unamortized debt discount and expense and other like intangibles, which in each case under GAAP would be included on the consolidated balance sheet.

“Funded Indebtedness” as applied to any Person, means all debt of that Person maturing after, or renewable or extendable at that Person’s option beyond, 12 months from the date of determination.

“Lien” means any lien, mortgage, pledge, encumbrance, charge or security interest securing debt; provided, however, that the following types of transactions will not be considered for purposes of this definition to result in a Lien: (1) any acquisition by us or any of our Restricted Subsidiaries of any property or assets subject to any reservation or exception under the terms of which any vendor, lessor or assignor creates, reserves or excepts or has created, reserved or excepted an interest in oil, gas or any other mineral in place or the proceeds thereof, (2) any conveyance or assignment whereby we or any Restricted Subsidiary convey or assign to any Person or Persons an interest in oil, gas or any other mineral in place or the proceeds thereof, (3) any Lien upon any property or assets either owned or leased by us or any Restricted Subsidiary or in which we or any Restricted Subsidiary own an interest that secures for the benefit of the Person or Persons paying the expenses of developing or conducting operations for the recovery, storage, transportation or sale of the mineral resources of the property or assets (or property or assets with which it is unitized) the payment to that Person or Persons of our or a Restricted Subsidiary’s proportionate part of such development or operating expenses or (4) any hedging arrangements entered into in the ordinary course of business, including any obligation to deliver any mineral, commodity or asset in connection therewith.

“Person” means any individual, corporation, partnership, limited liability company, joint venture, association, joint-stock company, trust, unincorporated organization or government or any agency or political subdivision thereof.

“Principal Property” means any property located in the United States, except any property that in the opinion of our board of directors is not of material importance to the total business conducted by us and our consolidated subsidiaries.

“Restricted Securities” means shares of stock or debt of any Restricted Subsidiary.

“Restricted Subsidiary” means any subsidiary that owns or leases Principal Property.

“Sale/Leaseback Transaction” means any arrangement with any Person pursuant to which we or any Restricted Subsidiary lease any Principal Property that has been or is to be sold or transferred by us to that Person, other than (1) a lease for a term, including renewals at the option of the lessee, of not more than three years or classified as an operating lease under GAAP, (2) leases between us and a Restricted Subsidiary or between Restricted Subsidiaries, (3) leases of a Principal Property executed by the time of, or within 12 months after the latest of, the acquisition, the completion of construction or improvement, or the commencement of commercial operation, of the Principal Property and (4) the ground lease for ONEOK Plaza, 100 West Fifth Street, Tulsa, Oklahoma 74103.

Consolidation, Merger and Sale of Assets

The Indentures generally permit a consolidation or merger between us and another entity. They also permit the sale by us of all or substantially all of our assets. We have agreed, unless we inform you otherwise in the

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prospectus supplement, however, that we will consolidate with or merge into any entity or transfer or dispose of all or substantially all of our assets to any entity only if:

Under the senior indenture, if we engage in any of these transactions that result in any Principal Property or shares of stock or debt of any Restricted Subsidiary becoming subject to any Lien and unless we are otherwise able to create that Lien, the senior debt securities (so long as those senior debt securities are entitled to the protection of the “Limitation on Liens” covenant) will be secured to at least the same extent as the debt that would become secured by the Lien as a result of the transaction.

Events of Default

Unless we inform you otherwise in the prospectus supplement, the following are events of default for a series of debt securities:

A default under one series of debt securities will not necessarily be a default under another series. The trustee may withhold notice to the holders of a series of debt securities of any default or event of default (except in any payment on that series of debt securities) if the trustee considers it in the interest of the holders of that series of debt securities to do so.

If an event of default for any series of debt securities occurs and is continuing, the trustee or the holders of at least 25% in principal amount of the outstanding debt securities of the series affected by the default (or, in some cases, 25% in principal amount of all debt securities affected, voting as one class) may require us to pay on an accelerated basis the principal of and all accrued and unpaid interest on those debt securities. The holders of a majority in principal amount of the outstanding debt securities of the series affected by the default (or of all debt securities affected, voting as one class) may in some cases rescind this accelerated payment requirement.

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If an event of default occurs and is continuing, the trustee must use the degree of care and skill of a prudent man in the conduct of his own affairs. The trustee will become obligated to exercise any of its powers under the applicable Indenture at the request of any of the holders of any debt securities only after those holders have offered the trustee indemnity reasonably satisfactory to it.

The holders of a majority in principal amount of debt securities of any series have the right to waive past defaults under the applicable Indenture that relate to that series except for a default in the payment on the debt securities or a provision that can only, under the applicable Indenture, be modified or amended if all holders that are affected consent.

In most cases, holders of a majority in principal amount of the outstanding debt securities of a series (or of all debt securities affected, voting as one class) may direct the time, method and place of:

The Indentures require us to file each year with the trustee a written statement as to our compliance with the covenants contained in the Indentures.

Modification and Waiver

We and each guarantor (if any) may amend or supplement either of the Indentures if the holders of a majority in principal amount of the outstanding debt securities of all series that the amendment or supplement affects (acting as one class) consent to it. Without the consent of the holder of each debt security affected, however, no modification may:

We and each guarantor (if any) may amend or supplement either of the Indentures or waive any provision of such Indenture without the consent of any holders of debt securities in various circumstances, including:

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The holders of a majority in principal amount of the outstanding debt securities under either Indenture may waive our obligations to comply with various covenants, including those relating to:

When we use the term defeasance, we mean discharge from some or all of our obligations under either Indenture. If we deposit with the trustee funds or government securities the maturing principal and interest of which is sufficient to make payments on the debt securities of a series on the dates those payments are due and payable, then, at our option, either of the following will occur:

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If we defease a series of debt securities, the holders of the debt securities of the series affected will not be entitled to the benefits of the applicable Indenture, to provide temporary debt securities, to register the transfer or exchange of debt securities, to replace stolen, lost or mutilated debt securities or to maintain paying agencies and hold money for payment in trust. In the case of covenant defeasance, our obligation to pay principal, premium and interest on the debt securities will also survive.

Unless we inform you otherwise in the prospectus supplement, we will be required to deliver to the trustee an opinion of counsel that the deposit and related defeasance would not cause the holders of the debt securities to recognize income, gain or loss for federal income tax purposes. If we elect legal defeasance, that opinion of counsel must be based upon a ruling from the Internal Revenue Service or a change in law to that effect.

Subordination Provisions for Subordinated Debt Securities

Any subordinated debt securities issued under the subordinated indenture will be subordinate and subject in right of payment to the prior payment in full of all of our Senior Indebtedness. The following provisions will apply to the subordinated debt securities unless otherwise specified in the prospectus supplement:

Subject to any collateral, security, assurance or guarantee provided for the benefit of any series of subordinated debt securities, if any, the payment of principal, any premium and interest on the subordinated debt securities will be subordinated in right of payment to the prior payment in full of all of our Senior Indebtedness. This means that in certain circumstances where we may not be making payments on all of our debt obligations as they become due, the holders of all of our Senior Indebtedness will be entitled to receive payment in full of all amounts that are due or will become due on the Senior Indebtedness before the holders of subordinated debt securities will be entitled to receive any payment or distribution (other than in the form of subordinated securities) on the subordinated debt securities. These circumstances include the following circumstances:

In addition, we are generally not permitted to make payments of principal, any premium or interest on the subordinated debt securities if we default on our obligation to make payments on our Senior Indebtedness and do not cure such default. We are also prohibited from making payments on subordinated debt securities if an event of default (other than a payment default) that permits the holders of senior indebtedness to accelerate the maturity of the Senior Indebtedness occurs and we and the trustee have received a notice of such event of default. However, unless the senior indebtedness has been accelerated because of that event of default, this payment blockage upon notice cannot last more than 179 days.

These subordination provisions mean that if we are insolvent a holder of Senior Indebtedness is likely to ultimately receive out of our assets more than a holder of the same amount of our subordinated debt securities, and a creditor of ours that is owed a specific amount but who owns neither our Senior Indebtedness nor our subordinated debt securities may ultimately receive less than a holder of the same amount of Senior Indebtedness and more than a holder of subordinated debt securities.

The subordinated indenture does not limit the amount of senior indebtedness we are permitted to have and we may in the future incur additional senior indebtedness.

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“Senior Indebtedness” is defined in the subordinated indenture to mean, with respect to us,

“Additional Junior Indebtedness” is defined in the subordinated indenture to mean, without duplication and other than the subordinated debt securities, any indebtedness, liabilities, guarantees or obligations of ours or any of our subsidiaries, under debt securities (or guarantees in respect of debt securities or preferred securities) initially issued after the date of the subordinated indenture to any trust, or a trustee of a trust, partnership or other entity affiliated with us that is, directly or indirectly, a finance subsidiary (as such term is defined in Rule 3a-5 under the Investment Company Act of 1940) or other financing vehicle of ours or any subsidiary of ours in connection with the issuance by that entity of preferred securities or other securities that are issued on a pari passu basis with the subordinated debt securities.

If this prospectus is being delivered in connection with a series of subordinated securities, the accompanying prospectus supplement or the information incorporated by reference will set forth the approximate amount of senior indebtedness outstanding as of a recent date.

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Guarantee

To the extent provided in a prospectus supplement and either a supplemental indenture or a resolution of our board of directors, in each case, relating to a particular series of debt securities, each of our subsidiaries that becomes a guarantor of the debt securities of such series, and any of our subsidiaries that is a successor thereto, will fully, irrevocably, unconditionally and absolutely guarantee the due and punctual payment of the principal of, and premium, if any, and interest on such debt securities, and all other amounts due and payable under the applicable indenture and such debt securities by us to the trustee or the holders of such debt securities, however, such guarantors will not otherwise be subject to the covenants, obligations and duties provided for in the indenture solely in their capacity as guarantors.

Satisfaction and Discharge

The Indentures will cease to be of further effect and will be deemed to have been satisfied and discharged with respect to a particular series of debt securities, when the following conditions have been satisfied:

Governing Law

New York law governs the Indentures and the debt securities.

Trustee

U.S. Bank National Association is trustee under the Indentures. The Indentures contain limitations on the right of the trustee, if it becomes one of our creditors, to obtain payment of claims or to realize payment on property received for those claims, as security or otherwise. The trustee is permitted to engage in other transactions with us in the ordinary course of business. If, however, it acquires any conflicting interest, it must eliminate that conflict or resign.

Form, Exchange, Registration and Transfer

We will issue the debt securities in registered form, without interest coupons. We will not charge a service charge for any registration of transfer or exchange of the debt securities. We may, however, require the payment of any tax or other governmental charge payable for that registration.

Holders may exchange debt securities of any series for other debt securities of the same series, the same total principal amount and the same terms but in different authorized denominations in accordance with the applicable Indenture. Holders may present debt securities for registration of transfer at the office of the security registrar or any transfer agent we designate. The security registrar or transfer agent will effect the transfer or exchange when it is satisfied with the documents of title and identity of the person making the request.

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We have appointed the trustee as security registrar for the debt securities. If a prospectus supplement refers to any transfer agent initially designated by us, we may at any time rescind that designation or approve a change in the location through which any transfer agent acts. We are required to maintain an office or agency for transfers and exchanges in each place of payment. We may at any time designate additional transfer agents for any series of debt securities.

In the case of any redemption, neither the security registrar nor the transfer agent will be required to register the transfer or exchange of any debt security either:

Payment and Paying Agents

Unless we inform you otherwise in a prospectus supplement, payments on the debt securities will be made in U.S. dollars at the office of the trustee. At our option, however, we may make payments by check mailed to the holder’s registered address or, for global debt securities, by wire transfer. Unless we inform you otherwise in a prospectus supplement, we will make interest payments to the person in whose name the debt security is registered at the close of business on the record date for the interest payment.

Unless we inform you otherwise in a prospectus supplement, we have designated the trustee as our paying agent for payments on debt securities issued under the Indentures. We may at any time designate additional paying agents or rescind the designation of any paying agent or approve a change in the office through which any paying agent acts.

Subject to the requirements of any applicable abandoned property laws, the trustee and paying agent will pay to us upon written request any money they are holding for payments on the debt securities that remain unclaimed for two years after the date upon which that payment has become due. After payment to us, holders entitled to the money must look to us for payment. In that case, all liability of the trustee or paying agent with respect to that money will cease.

Book-Entry Debt Securities

We may issue the debt securities of a series in the form of one or more global debt securities that would be deposited with a depositary or its nominee identified in the prospectus supplement. We may issue global debt securities in either temporary or permanent form. We will describe in the prospectus supplement the terms of any depositary arrangement and the rights and limitations of owners of beneficial interests in any global debt security.

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DESCRIPTION OF GUARANTEE OF DEBT SECURITIES

To the extent provided in a prospectus supplement and either an indenture supplement or a resolution of our board of directors, in each case, relating to a particular series of debt securities, each of our subsidiaries that becomes a guarantor of the debt securities of such series, and any of our subsidiaries that is a successor thereto, will fully, irrevocably, unconditionally and absolutely guarantee the due and punctual payment of the principal of, and premium, if any, and interest on such debt securities, and all other amounts due and payable under the applicable indenture and such debt securities by us to the trustee or the holders of such debt securities, and any provisions permitting a release of such guarantee will be included in such prospectus supplement and indenture supplement or resolution, however, such guarantors will not otherwise be subject to the covenants, obligations and duties provided for in the indenture solely in their capacity as guarantors.

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DESCRIPTION OF CAPITAL STOCK

General

We are authorized to issue a total of 1,300,000,000 shares of all classes of capital stock. Of those authorized shares, 1,200,000,000 are shares of common stock, 379,927,619 shares of which were outstanding as of July 3, 2017, and 100,000,000 are shares of preferred stock. Of the authorized preferred stock, there are 20,000,000 shares designated as Convertible Preferred Stock, Series A (none of which was outstanding on July 3, 2017), 30,000,000 shares designated as Convertible Preferred Stock, Series B (none of which was outstanding on July 3, 2017), 1,000,000 shares designated as Series C Participating Preferred Stock (none of which was outstanding on July 3, 2017), and 20,000 shares designated as Series E Non-Voting Perpetual Preferred Stock (all of which were outstanding on July 3, 2017).

The additional shares of our authorized stock available for issuance might be issued at times and under circumstances so as to have a dilutive effect on earnings per share and on the equity ownership of the holders of our common stock. The ability of our board of directors to issue additional shares of stock could enhance the board’s ability to negotiate on behalf of the shareholders in a takeover situation but could also be used by the board to make a change-in-control more difficult, thereby denying shareholders the potential to sell their shares at a premium and entrenching current management.

The following description is a summary of the material provisions of our capital stock and various provisions of our certificate of incorporation and bylaws. This summary is not intended to be complete and is qualified by reference to the provisions of applicable law and our certificate of incorporation and bylaws included as exhibits to the registration statement of which this prospectus is a part.

Common Stock

As of July 3, 2017, there were 13,514 holders of record. The issued and outstanding shares of common stock are validly issued, fully paid and non-assessable. Subject to any preferential rights of any prior ranking class or series of capital stock, including the preferred stock, holders of our common stock are entitled to receive dividends on that stock, payable either in cash, property or shares out of assets legally available for distribution when, as and if authorized and declared by our board of directors and to share ratably in our assets legally available for distribution to our shareholders in the event of liquidation, dissolution or winding-up. Subject to various exceptions, we will not be able to pay any dividend or make any distribution of assets on shares of our common stock until we pay dividends on any shares of preferred stock then outstanding with dividend or distribution rights senior to our common stock.

Holders of our common stock are entitled to one vote per share on all matters voted on by our shareholders, including the election of directors. Our certificate of incorporation does not provide for cumulative voting for the election of directors, which means that holders of more than one-half of the outstanding shares of our voting securities will be able to elect all of the directors then standing for election and holders of the remaining shares will not be able to elect any director.

Our board of directors may make rules and regulations concerning the transfer of shares of our common stock from time to time, in accordance with our bylaws.

Holders of our common stock will have no conversion, sinking fund or redemption rights.

Some provisions of the Oklahoma General Corporation Act, our certificate of incorporation and our bylaws may discriminate against holders of a substantial amount of the shares of our common stock. See “—Oklahoma Law” and “—Certificate of Incorporation and Bylaws.” Similarly, some provisions of our certificate of incorporation and our bylaws may have the effect of delaying, deferring or preventing a change-in-control with respect to an extraordinary corporate transaction, such as a merger, reorganization, tender offer, sale or transfer of substantially all of our assets.

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Preferred Stock

Our board of directors is authorized to issue shares of preferred stock, in one or more series or classes, and to fix for each series or class the preferences, conversion or other rights, voting powers, restrictions, limitations as to dividends, qualifications, or terms or redemption, as are permitted by Oklahoma law and as are stated in the resolution or resolutions adopted by the board providing for the issuance of shares of that series or class.

Our board has authorized series designated as Convertible Preferred Stock, Series A and Convertible Preferred Stock, Series B. Our board has also authorized a series designated as Series C Participating Preferred Stock, which relates to our Second Amended and Restated Rights Agreement. No shares of Series C Participating Preferred Stock were issued, and the Second Amended and Restated Rights Agreement expired February 4, 2013, and was not renewed. Our board has further authorized a series of preferred stock designated as Series E Non-Voting Perpetual Preferred Stock, which is expected to pay quarterly dividends on each share, when, as and if declared by our board, at a rate of 5.5% per year. In April 2017, through a wholly owned subsidiary, we issued and contributed 20,000 shares of Series E Preferred Stock to ONEOK Foundation, Inc. for use in future charitable and nonprofit causes. No other shares of Series E Non-Voting Perpetual Preferred Stock have been issued.

When we offer to sell a particular series of preferred stock, we will describe the specific terms of the securities in a supplement to this prospectus. The prospectus supplement will also indicate whether the terms and provisions described in this prospectus apply to the particular series of preferred stock. The preferred stock will be issued under a certificate of designations relating to each series of preferred stock. The issuance of our preferred stock is also subject to our certificate of incorporation.

Preemptive Rights

No holder of any shares of any class of our stock has any preemptive or preferential right to acquire or subscribe for any unissued shares of any class of stock or any unauthorized securities, convertible into or carrying any right, option or warrant to subscribe for or acquire shares of any class of stock.

Oklahoma Law

Oklahoma Takeover Statute

We are subject to Section 1090.3 of the Oklahoma General Corporation Act. In general, Section 1090.3 prevents an “interested shareholder” from engaging in a “business combination” with an Oklahoma corporation for three years following the date that person became an interested shareholder, unless:

Section 1090.3 defines a “business combination” to include:

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For purposes of the description above and Section 1090.3, the term “corporation” also includes our majority-owned subsidiaries. In addition, Section 1090.3, defines an “interested shareholder” as an entity or person beneficially owning 15% or more of our outstanding voting stock and any entity or person affiliated with or controlling or controlled by that entity or person.

Oklahoma Control Share Provisions

Our certificate of incorporation provides that we are not subject to the control share provisions of the Oklahoma General Corporation Act. With exceptions, these provisions prevent holders of more than 20% of the voting power of the stock of an Oklahoma corporation from voting their shares. If we were to become subject to the control share provisions of the Oklahoma General Corporation Act in the future, this provision may delay the time it takes anyone to gain control of us.

Certificate of Incorporation and Bylaws

Exculpation

Our certificate of incorporation provides that our directors and officers will not be personally liable for monetary damages for any action taken, or any failure to take any action, unless:

Indemnification

We will generally indemnify any person who was, is, or is threatened to be made, a party to a proceeding by reason of the fact that he or she:

Any indemnification of our directors, officers or others pursuant to the foregoing provisions for liabilities arising under the Securities Act are, in the opinion of the SEC, against public policy as expressed in the Securities Act and are unenforceable.

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Shareholder Action; Special Meeting of Shareholders

Our certificate of incorporation eliminates the ability of our shareholders to act by written consent. Our bylaws provide that special meetings of our shareholders may be called only by a majority of the members of our board of directors.

Advance Notice Requirements for Shareholder Proposals

At any annual meeting of our shareholders, the only business that shall be brought before the meeting is that which is brought:

For business to be properly brought before an annual meeting by a shareholder pursuant to the immediately preceding clause, the shareholder must have given timely notice in writing to our secretary. To be timely as to an annual meeting of shareholders, a shareholder’s notice must be received at our principal executive offices not less than 120 calendar days before the date our proxy statement is released to shareholders in connection with the previous year’s annual meeting; provided however, that if the date of the meeting is changed by more than 30 days from the date of the previous year’s meeting, notice must be received no later than the close of business on the 10th day following the earlier of the day on which notice of the date of the meeting was mailed to shareholders or public disclosure of that date was made. The shareholder notice shall set forth as to each matter the shareholder proposes to bring before the meeting:

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These provisions may impede shareholders’ ability to bring matters before an annual meeting of shareholders.

Higher Vote for Some Business Combinations and Other Actions

Subject to various exceptions, including acquiring 85% of the outstanding shares less shares owned by related persons in a single transaction, a business combination (including, but not limited to, a merger or consolidation, the sale, lease, exchange, mortgage, pledge, transfer or other disposition of our assets in excess of $5,000,000, various issuances and reclassifications of securities and the adoption of a plan or proposal for liquidation or dissolution) with or upon a proposal by a related person, who is a person that is the direct or indirect beneficial owner of more than 10% of the outstanding voting shares of our stock (subject to various exceptions), and any affiliates of that person, shall require, in addition to any approvals required by law, the approval of the business combination by either:

In addition, our certificate of incorporation provides that our bylaws may only be adopted, amended or repealed by a majority of the board of directors or by 80% of our shareholders, voting as a class. Our certificate of incorporation also requires the affirmative vote of 80% of our shareholders to amend, repeal or adopt provisions in our certificate of incorporation relating to, among other things,

Transactions with Interested Parties

Our certificate of incorporation provides that, in the absence of fraud, no contract or other transaction will be affected or invalidated by the fact that any of our directors are in any way interested in or connected with any other party to the contract or transaction or are themselves parties to the contract or transaction, provided that the interest is fully disclosed or otherwise known to our board of directors at the meeting of the board at which the contract or transaction is authorized or confirmed, and provided further that a quorum of disinterested directors is

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present at the meeting of our board of directors authorizing or confirming the contract or transaction and the contract or transaction is approved by a majority of the quorum, and no interested director votes on the contract or transaction. Any contract, transaction or act entered into or taken by us or our board or any committee thereof that is ratified by a majority of a quorum of the shareholders having voting power at any annual meeting, or any special meeting called for that purpose, will be valid and binding as though ratified by all of our shareholders. Any director may vote upon any contract or other transaction between us and any subsidiary corporation without regard to the fact that he is also a director of that subsidiary corporation. No contract or agreement between us and any other corporation or party that owns a majority of our capital stock or any subsidiary of that other corporation shall be made or entered into without the affirmative vote of a majority of the whole board of directors at a regular meeting of the board.

Transfer Agent and Registrar

The current transfer agent and registrar for our common stock is Wells Fargo Shareholder Services, a division of Wells Fargo Bank, N.A.

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DESCRIPTION OF STOCK PURCHASE CONTRACTS

AND STOCK PURCHASE CONTRACT UNITS

We may issue stock purchase contracts for the purchase of our securities or securities of an entity unaffiliated or affiliated with us, a basket of such securities or any combination of the above as specified in the applicable prospectus supplement. Each stock purchase contract will entitle the holder thereof to purchase, and obligate us to sell, on specified dates, such securities, at a specified purchase price, all as set forth in the applicable prospectus supplement. The applicable prospectus supplement will also specify the methods by which the holders may purchase such securities, any acceleration, cancellation or termination provisions or other provisions relating to the settlement of a stock purchase contract and, if applicable, the identity of any of our subsidiaries guaranteeing our obligations with respect to such stock purchase contracts. Stock purchase contracts may require holders to satisfy their obligations thereunder when the stock purchase contracts are issued. Our obligation to settle such prepaid stock purchase contracts on the relevant settlement date may constitute indebtedness. Accordingly, the prepaid stock purchase contracts will be issued under one of the Indentures. The stock purchase contracts may be issued separately or as part of a stock purchase contract unit that consists of (a) a stock purchase contract and (b) senior or subordinated debt securities, or preferred stock, U.S. Treasury securities or other debt obligations of third parties, that may be used to secure the holders’ obligations under a stock purchase contract. The stock purchase contracts may require us to make periodic payments to the holders of the stock purchase contract units, and such payments may be unsecured or prefunded on some basis. The stock purchase contracts may require holders to secure their obligations in a specified manner and, in certain circumstances, we may deliver newly issued prepaid stock purchase contracts upon release to a holder of any collateral securing such holder’s obligations under the original stock purchase contract.

The applicable prospectus supplement will describe the general terms of any stock purchase contracts or stock purchase contract units and, if applicable, prepaid stock purchase contracts. The description in the prospectus supplement will not purport to be complete and will be qualified in its entirety by reference to (a) the stock purchase contracts, (b) the collateral arrangements and depository arrangements, if applicable, relating to such stock purchase contracts or stock purchase contract units and (c) if applicable, the prepaid stock purchase contracts and the documents pursuant to which such prepaid stock purchase contracts will be issued. Some of the material United States federal income tax considerations applicable to the stock purchase contracts and the stock purchase contract units will also be discussed in the applicable prospectus supplement.

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DESCRIPTION OF DEPOSITARY SHARES

General

We may, at our option, elect to offer fractional shares of preferred stock, rather than full shares of preferred stock. If we exercise this option, we will issue to the public receipts for depositary shares, and each of these depositary shares will represent a fraction (to be set forth in the applicable prospectus supplement) of a share of a particular series of preferred stock.

The shares of any series of preferred stock underlying the depositary shares will be deposited under a deposit agreement between us and a bank or trust company selected by us. The depositary will have its principal office in the United States and a combined capital of at least $50,000,000. Subject to the terms of the deposit agreement, each owner of a depositary share will be entitled, in proportion, to the applicable fraction of a share of preferred stock underlying that depositary share, to all the rights and preferences of the preferred stock underlying that depositary share. Those rights (to be set forth in the applicable prospectus supplement) include dividend, voting, redemption and liquidation rights.

The depositary shares will be evidenced by depositary receipts issued pursuant to the deposit agreement. Depositary receipts will be distributed to those persons purchasing the fractional shares of preferred stock underlying the depositary shares, in accordance with the terms of the offering. Copies of the forms of deposit agreement and depositary receipt will be filed as exhibits to the registration statement. The following summary of the deposit agreement, the depositary shares and the depositary receipts is not complete. You should refer to the forms of the deposit agreement and depositary receipts that will be filed with the SEC in connection with the offering of the specific depositary shares.

Pending the preparation of definitive engraved depositary receipts, the depositary may, upon our written order, issue temporary depositary receipts substantially identical to the definitive depositary receipts but not in definitive form. These temporary depositary receipts entitle their holders to all the rights of definitive depositary receipts which are to be prepared without unreasonable delay. Temporary depositary receipts will then be exchangeable for definitive depositary receipts at our expense.

Dividends and Other Distributions

The depositary will distribute all cash dividends or other cash distributions received with respect to the preferred stock to the record holders of depositary shares relating to the preferred stock in proportion to the number of depositary shares owned by those holders.

If there is a distribution other than in cash, the depositary will distribute property received by it to the record holders of depositary shares that are entitled to receive the distribution, unless the depositary determines that it is not feasible to make the distribution. If this occurs, the depositary may, with our approval, sell the property and distribute the net proceeds from the sale to the applicable holders.

Redemption of Depositary Shares

If a series of preferred stock represented by depositary shares is subject to redemption, the depositary shares will be redeemed from the proceeds received by the depositary resulting from the redemption, in whole or in part, of that series of preferred stock held by the depositary. The redemption price per depositary share will be equal to the applicable redemption fraction of the redemption price per share payable with respect to that series of the preferred stock. Whenever we redeem shares of preferred stock that are held by the depositary, the depositary will redeem, as of the same redemption date, the number of depositary shares representing the shares of preferred stock so redeemed. If fewer than all the depositary shares are to be redeemed, the depositary shares to be redeemed will be selected by lot or pro rata as may be determined by the depositary.

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Voting the Preferred Stock

Upon receipt of notice of any meeting at which the holders of the preferred stock are entitled to vote, the depositary will mail the information contained in such notice to the record holders of the depositary shares underlying the preferred stock. Each record holder of the depositary shares on the record date, which will be the same date as the record date for the preferred stock, will be entitled to instruct the depositary as to the exercise of the voting rights pertaining to the amount of the preferred stock represented by the holder’s depositary shares. The depositary will then try, as far as practicable, to vote the number of shares of preferred stock underlying those depositary shares in accordance with such instructions. We will agree to take all actions which may be deemed necessary by the depositary to enable the depositary to do so. The depositary will not vote the shares of preferred stock to the extent it does not receive specific instructions from the holders of depositary shares underlying the preferred stock.

Amendment and Termination of the Depositary Agreement

The form of depositary receipt evidencing the depositary shares and any provision of the deposit agreement may at any time be amended by agreement between us and the depositary. However, any amendment which materially and adversely alters the rights of the holders of depositary shares will not be effective unless the amendment has been approved by the holders of at least a majority of the depositary shares then outstanding. The deposit agreement may be terminated by us or by the depositary only if (a) all outstanding depositary shares have been redeemed or (b) there has been a final distribution of the underlying preferred stock in connection with our liquidation, dissolution or winding up and the preferred stock has been distributed to the holders of depositary receipts.

Charges of Depositary

We will pay all transfer and other taxes and governmental charges arising solely from the existence of the depositary arrangements. We will also pay charges of the depositary in connection with the initial deposit of the preferred stock and any redemption of the preferred stock. Holders of depositary receipts will pay other transfer and other taxes and governmental charges and those other charges, including a fee for the withdrawal of shares of preferred stock upon surrender of depositary receipts, as are expressly provided in the deposit agreement to be for their accounts.

Miscellaneous

The depositary will forward to holders of depositary receipts all reports and communications from us that we deliver to the depositary and that we are required to furnish to the holders of the preferred stock.

Neither we nor the depositary will be liable if either of us is prevented or delayed by law or any circumstance beyond our control in performing our respective obligations under the deposit agreement. Our obligations and those of the depositary will be limited to performance in good faith of our respective duties under the deposit agreement. Neither we nor the depositary will be obligated to prosecute or defend any legal proceeding in respect of any depositary shares or preferred stock unless satisfactory indemnity is furnished. We and the depositary may rely upon written advice of counsel or accountants, or upon information provided by persons presenting preferred stock for deposit, holders of depositary receipts or other persons believed to be competent and on documents believed to be genuine.

Resignation and Removal of Depositary

The depositary may resign at any time by delivering notice to us of its election to resign. We may remove the depositary at any time. Any resignation or removal will take effect upon the appointment of a successor depositary and its acceptance of the appointment. The successor depositary must be appointed within 60 days after delivery of the notice of resignation or removal and must be a bank or trust company having its principal office in the United States and having a combined capital and surplus of at least $50,000,000.

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DESCRIPTION OF WARRANTS

We may issue warrants for the purchase of debt securities, preferred stock, common stock, or units of two or more of these types of securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and a bank or trust company, as warrant agent. The warrant agent will act solely as our agent in connection with the warrants and will not assume any obligation or relationship of agency or trust for or with any registered holders of warrants or beneficial owners of warrants.

We will distribute a prospectus supplement with regard to each issue of warrants. Each prospectus supplement will describe:

Warrants for the purchase of preferred stock and common stock will be offered and exercisable for U.S. dollars only. Warrants will be issued in registered form only. The exercise price for warrants will be subject to adjustment as described in the applicable prospectus supplement.

Prior to the exercise of any warrants to purchase debt securities, preferred stock or common stock, holders of the warrants will not have any of the rights of holders of the debt securities, preferred stock or common stock purchasable upon exercise, including:

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PLAN OF DISTRIBUTION

We may sell our securities through agents, underwriters or dealers, or directly to purchasers.

We may designate agents to solicit offers to purchase our securities.

We may use one or more underwriters in the offer or sale of our securities.

We may use a dealer to sell our securities.

We may directly solicit offers to purchase our securities, and we may directly sell our securities to institutional or other investors. We will describe the terms of our direct sales in our prospectus supplement.

We may indemnify agents, underwriters and dealers against certain liabilities, including liabilities under the Securities Act.

We may authorize our agents and underwriters to solicit offers by certain institutions to purchase our securities at the public offering price under delayed delivery contracts.

Underwriters, dealers and agents and their affiliates may engage in transactions with, or perform services for, or be customers of ONEOK and its affiliates in the ordinary course of business.

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Other than our common stock, all securities offered by this prospectus will be a new issue of securities with no established trading market. Any underwriter to whom securities are sold by us for public offering and sale may make a market in such securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. The securities may or may not be listed on a national securities exchange or a foreign securities exchange, except for the common stock which is currently listed and traded on the New York Stock Exchange. Any common stock sold by this prospectus will be listed for trading on the New York Stock Exchange subject to official notice of issuance. We cannot give you any assurance as to the liquidity of the trading markets for any securities.

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LEGAL MATTERS

The validity of the securities being offered hereby will be passed upon for us by GableGotwals, Tulsa, Oklahoma, except that Fried, Frank, Harris, Shriver  & Jacobson LLP, New York, New York, will pass upon such matters to the extent governed by New York law.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control over Financial Reporting) incorporated in this Prospectus by reference to ONEOK, Inc.’s Current Report on Form 8-K dated July 6, 2017 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

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