Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN 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. Issuer Name and Ticker or Trading Symbol
IRONWOOD PHARMACEUTICALS INC [IRWD] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) __X__ Other (specify below)
Edward C. Johnson 3d
(Last)
(First)
(Middle)
82 DEVONSHIRE STREET		 3. Date of Earliest Transaction (Month/Day/Year)
09/13/2012
(Street)

BOSTON, MA 02109		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Class A Common Stock 09/13/2012   S   29,514 D $ 13.0613 (2) 2,089,460 I See Footnote (1)
Class A Common Stock 09/14/2012   S   84,925 D $ 13.1377 (3) 2,004,535 I See Footnote (1)
Class A Common Stock 09/17/2012   S   39,337 D $ 13.2168 1,965,198 I See Footnote (1)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
FMR LLC
82 DEVONSHIRE STREET
BOSTON, MA 02109		     X   Edward C. Johnson 3d
FIL Ltd
P.O. BOX H.M. 670
HAMILTON, D0 00000		     X   Edward C. Johnson 3d

Signatures

 Scott C. Goebel, Duly authorized under Powers of Attorney effective as of June 1, 2008, by and on behalf of FMR LLC and its direct and indirect subsidiaries, by and on behalf of Edward C. Johnson 3d, and by and on behalf of FIL Limited   09/17/2012
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(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) 1. Column 5 Amount of Securities Beneficially Owned Following Reported Transaction is held by Impresa Fund II LLC (654,496 Class A Common Stock), Impresa Fund III Limited Partnership (74,798 Class A Common Stock), Fidelity Biosciences Corp. (10,971 Class A Common Stock) and FIL Limited (1,224,933 Class A Common Stock). Column 5 does not include shares beneficially owned by Fidelity Management & Research Company as a result of acting as investment adviser to various investment companies as disclosed in Remark 1 below.
(2) The price reported for this transaction is the weighted average price of multiple trades at prices ranging from $13.0137 to $13.0675. FMR LLC hereby undertakes to provide upon request by the Commission staff, the issuer, or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.
(3) The price reported for this transaction is the weighted average price of multiple trades at prices ranging from $13.1313 to $13.1404. FMR LLC hereby undertakes to provide upon request by the Commission staff, the issuer, or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.
 
Remarks:
Remark 1: Fidelity Management & Research Company, a wholly owned subsidiary of FMR LLC and an investment adviser registered under the Investment Advisers Act of 1940, is the beneficial owner of Class A Common Stock of Ironwood Pharmaceuticals Inc. as a result of acting as investment adviser to various investment companies registered under the Investment Company Act of 1940. FMR LLC, Edward C. Johnson 3d and FIL Limited have no pecuniary interest in the Class A Common Stock beneficially owned by Fidelity Management & Research Company. Remark 2: FIL Limited directly holds 1,224,933 shares of Class A Common Stock of Ironwood Pharmaceuticals Inc. FMR LLC and FIL are of the view that they are not acting as a "group" for purposes of Section 13(d) under the Securities Exchange Act of 1934 (the "1934 Act") and that they are not otherwise required to attribute to each other the "beneficial ownership" of securities "beneficially owned" by the other corporation within the meaning of Rule 16a-1 promulgated under the 1934 Act. Therefore, they are of the view that the shares held by the other corporation need not be aggregated for purposes of Section 16(a). However, FMR LLC is making this filing on a voluntary basis as if all of the shares are beneficially owned by FMR LLC and FIL on a joint basis.

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