Ownership Submission
FORM 3
 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
  FMR LLC
 2. Date of Event Requiring Statement (Month/Day/Year)
09/22/2015		 3. Issuer Name and Ticker or Trading Symbol
REGENXBIO Inc. [RGNX]
(Last)
(First)
(Middle)
245 SUMMER STREET		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) __X__ Other (specify below)
See Remark 1
 5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

BOSTON, MA 02210		 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security
(Instr. 4)		 2. Amount of Securities Beneficially Owned
(Instr. 4)		 3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)		 4. Nature of Indirect Beneficial Ownership
(Instr. 5)
Common Stock 1,085,816 (1)
I
Beacon Bioventures Fund III Limited Partnership

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 4)		 2. Date Exercisable and Expiration Date
(Month/Day/Year)		 3. Title and Amount of Securities Underlying Derivative Security
(Instr. 4)		 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 5)		 6. Nature of Indirect Beneficial Ownership
(Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
FMR LLC
245 SUMMER STREET
BOSTON, MA 02210		     X   See Remark 1

Signatures

Scott C. Goebel, Duly authorized under Powers of Attorney, by and on behalf of FMR LLC and its direct and indirect subsidiaries, Edward C. Johnson 3d and Abigail P. Johnson 09/25/2015
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 5(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) FMR Co., Inc., an indirect wholly-owned subsidiary of FMR LLC and an investment adviser registered under the Investment Advisers Act of 1940, and Pyramis Global Advisors Trust Company, an indirect wholly-owned subsidiary of FMR LLC and a bank as defined in Section 3(a)(6) of the Securities Exchange Act of 1934, are the beneficial owners of 1,629,620 shares, or 6.43%, of Common Stock of REGENXBIO Inc., as a result of acting as investment adviser to various investment companies registered under the Investment Company Act of 1940, institutional accounts and non-U.S. mutual funds. FMR LLC, Edward C. Johnson 3d and Abigail P. Johnson have no pecuniary interest in the 1,629,620 shares of Common Stock and Table 1, Column 2 does not include such shares.
 
Remarks:
Remark 1: Edward C. Johnson 3d is a Director and the Chairman of FMR LLC and Abigail P. Johnson is a Director, the Vice Chairman and the President of FMR LLC. Members of the family of Edward C. Johnson 3d, including Abigail P. Johnson, are the predominant owners, directly or through trusts, of Series B voting common shares of FMR LLC, representing 49% of the voting power of FMR LLC. The Johnson family group and all other Series B shareholders have entered into a shareholders' voting agreement under which all Series B voting common shares will be voted in accordance with the majority vote of Series B voting common shares. Accordingly, through their ownership of voting common shares and the execution of the shareholders' voting agreement, members of the Johnson family may be deemed, under the Investment Company Act of 1940, to form a controlling group with respect to FMR LLC. The address of Edward C. Johnson 3d and Abigail P. Johnson is c/o FMR LLC, 245 Summer Street, Boston, MA 02110.


Remark 2: Beacon Bioventures Advisors Fund III Limited Partnership is the general partner of Beacon Bioventures  Fund III Limited Partnership. Beacon Bioventures Advisors Fund III Limited Partnership is solely managed by Impresa Management LLC, its general partner and investment manager. Impresa Management LLC is owned, directly or indirectly, by various shareholders and employees of FMR LLC, including certain members of the family of Edward C. Johnson 3d.

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