Exhibit 5.1

Sean M. Clayton

T: +1 858 550 6034

sclayton@cooley.com

March 18, 2013

MannKind Corporation

28903 North Avenue Paine

Valencia, CA 91355

Ladies and Gentlemen:

You have requested our opinion with respect to certain matters in connection with the offering by MannKind Corporation, a Delaware corporation (the “Company”), of the lesser of (i) $50,000,000 of shares or (ii) 25,000,000 shares of the Company’s common stock, par value $0.01 (the “Shares”), pursuant to a Registration Statement on Form S-3 (No. 333-183679) (the “Registration Statement”), filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”), the prospectus included within the Registration Statement (the “Base Prospectus”), and the prospectus supplement dated March 18, 2013, filed with the Commission pursuant to Rule 424(b) of the Rules and Regulations of the Act (the “Prospectus Supplement”). The Base Prospectus and the Prospectus Supplement are collectively referred to as the “Prospectus.” The Shares are to be sold by the Company in accordance with (i) an At-The-Market Issuance Sales Agreement, dated March 18, 2013, between the Company and MLV & Co. LLC (the “MLV Agreement”) and (ii) an At-The-Market Issuance Sales Agreement, dated March 18, 2013, between the Company and Brinson Patrick Securities Corporation (the “Brinson Patrick Agreement”), as described in the Prospectus.

In connection with this opinion, we have examined and relied upon the Registration Statement and the Prospectus, the MLV Agreement, the Brinson Patrick Agreement, the Company’s Amended and Restated Certificate of Incorporation, as amended, its Amended and Restated Bylaws, and the originals or copies certified to our satisfaction of such records, documents, certificates, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below. In rendering this opinion, we have assumed the genuineness and authenticity of all signatures on original documents; the genuineness and authenticity of all documents submitted to us as originals; the conformity to originals of all documents submitted to us as copies; the accuracy, completeness and authenticity of certificates of public officials; and the due authorization, execution and delivery of all documents where due authorization, execution and delivery are prerequisites to the effectiveness of such documents.

Our opinion herein is expressed solely with respect to the federal laws of the United States of America and the General Corporation Law of the State of Delaware. Our opinion is based on these laws as in effect on the date hereof. We express no opinion as to whether the laws of any particular jurisdiction other than those identified above are applicable to the subject matter hereof.

4401 EASTGATE MALL, SAN DIEGO, CA 92121 T: (858) 550-6000 F: (858) 550-6420 WWW.COOLEY.COM

MannKind Corporation

March 18, 2013

Page Two

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when sold and issued against payment therefor in accordance with the MLV Agreement or the Brinson Patrick Agreement, as applicable, the Registration Statement and the Prospectus, will be validly issued, fully paid and nonassessable.

We consent to the reference to our firm under the caption “Legal Matters” in the Prospectus and to the filing of this opinion as an exhibit to the Company’s Annual Report on Form 10-K for the year ended December 31, 2012 to be filed with the Commission for incorporation by reference into the Registration Statement.

Very truly yours,
Cooley LLP
By:	/s/ Sean M. Clayton
	Sean M. Clayton

4401 EASTGATE MALL, SAN DIEGO, CA 92121 T: (858) 550-6000 F: (858) 550-6420 WWW.COOLEY.COM