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 *
  Flynn James E
 2. Date of Event Requiring Statement (Month/Day/Year)
05/08/2018		 3. Issuer Name and Ticker or Trading Symbol
Mallinckrodt plc [MNK]
(Last)
(First)
(Middle)
780 THIRD AVENUE, 37TH FLOOR, 		 4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director __X__ 10% Owner
_____ Officer (give title below) __X__ Other (specify below)
*Possible member of 10% group
 5. If Amendment, Date Original Filed(Month/Day/Year)
(Street)

NEW YORK, NY 10017		 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 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)
Ordinary Shares, $0.20 par value 8,621,383
I
Through Deerfield Partners, L.P. (1) (2)

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
Cash-Settled Total Return Swap   (3) 06/28/2021 Ordinary Shares, $0.20 par value 1,701,177 $ 12.98 (4) I Through Deerfield Partners, L.P. (1) (2)
Cash-Settled Total Return Swap   (3) 03/20/2023 Ordinary Shares, $0.20 par value 1,249,379 $ 14.48 (4) I Through Deerfield Partners, L.P. (1) (2)

Reporting Owners

Reporting Owner Name / Address Relationships
Director 10% Owner Officer Other
Flynn James E
780 THIRD AVENUE, 37TH FLOOR
NEW YORK, NY 10017		     X   *Possible member of 10% group
Deerfield Mgmt L.P.
780 THIRD AVENUE
37TH FLOOR
NEW YORK, NY 10017		     X   *Possible member of 10% group
DEERFIELD MANAGEMENT COMPANY, L.P. (SERIES C)
780 THIRD AVENUE, 37TH FLOOR
NEW YORK, NY 10017		     X   *Possible member of 10% group
DEERFIELD PARTNERS, L.P.
780 THIRD AVENUE
37TH FLOOR
NEW YORK, NY 10017		     X   *Possible member of 10% group

Signatures

/s/ Jonathan Isler, Attorney-in-Fact 05/10/2018
**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) This Form 3 is being filed by the undersigned as well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). Deerfield Mgmt, L.P. is the general partner of Deerfield Partners, L.P. (the "Fund"). Deerfield Management Company, L.P. is the investment manager of the Fund. James E. Flynn is the sole member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P.
(2) In accordance with Instruction 5(b)(iv) to Form 3, the entire amount of the Issuer's securities (and derivative securities with respect thereto) held by the Fund is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.
(3) The Fund has entered into certain cash-settled total return swap agreements with unaffiliated third party financial institutions, which provide the Fund with economic exposure to an aggregate of 2,950,556 notional shares. Each swap agreement provides the Fund with economic results that are comparable to the economic results of ownership of, but do not provide the Fund with the power to vote or direct the voting of, or dispose of or direct the disposition of, the ordinary shares that are the subject of such swap agreement.
(4) Represents the reference price associated with the applicable swap agreement.
 
Remarks:
Jonathan Isler, Attorney-in-Fact: Power of Attorney, which is hereby incorporated by reference to Exhibit 24 to a Form 3 with regard to Proteon Therapeutics, Inc. filed with the Securities and Exchange Commission on August 4, 2017 by Deerfield Special Situations Fund, L.P., Deerfield Partners, L.P., Deerfield International Master Fund, L.P., Deerfield Private Design Fund III, L.P., Deerfield Private Design Fund IV, L.P., Deerfield Mgmt, L.P., Deerfield Mgmt III, L.P., Deerfield Mgmt IV, L.P., Deerfield Management Company, L.P., and James E. Flynn.

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