Exhibit 5.1


Mayer Brown LLP700 Louisiana Street Suite 3400 Houston, Texas 77002-2730Main Tel +1 713 238 3000 Main Fax +1 713 238 4888www.mayerbrown.comOctober 24, 2013Noble Energy, Inc.1001 Noble Energy WayHouston, Texas  77070





Ladies and Gentlemen:





We have acted as special counsel to Noble Energy, Inc. (the “Company”), in connection with the registration under the Securities Act of 1933, as amended (the “Securities Act”), of 9,600,000 shares of the Company’s common stock, par value $0.01 per share (the “Shares”), for issuance and sale pursuant to the Noble Energy, Inc. 1992 Stock Option and Restricted Stock Plan, as amended (the “1992 Plan”). We have participated in the preparation of the Company’s Registration Statement on Form S-8 (the “Registration Statement”), filed on this date with the Securities and Exchange Commission (the “Commission”), relating to the registration of the Shares under the Securities Act.





In connection therewith, we have reviewed copies of the relevant corporate resolutions of the Company and have examined originals or copies, certified or otherwise identified to our satisfaction, of such corporate records and documents as we have deemed necessary as a basis for the opinions hereinafter expressed.





We have assumed the authenticity and completeness of all records, certificates and other instruments submitted to us as originals, the conformity to the original documents of all records, certificates and other instruments submitted to us as copies, the authenticity and completeness of the originals of those records, certificates and other instruments submitted to us as copies and the correctness of all statements of fact contained in all records, certificates and other instruments that we have examined.





Based on the foregoing and subject to the qualifications set forth herein, we are of opinion that the issuance of the Shares has been duly authorized and, when issued, delivered and fully paid for in accordance with the terms of the Registration Statement and the 2012 Plan, such Shares will be validly issued, fully paid and nonassessable.





Our opinion is limited to the General Corporation Law of the State of Delaware (including the applicable provisions of the Delaware Constitution and the reported judicial decisions interpreting these laws) and the federal laws of the United States of America. We are expressing no opinion as to the effect of the laws of any other jurisdiction, domestic or foreign.





The opinions and statements expressed herein are as of the date hereof. We assume no obligation to update or supplement this opinion letter to reflect any facts or circumstances that may hereafter come to our attention or any changes in applicable law which may hereafter occur.





We hereby consent to the filing of this opinion with the Commission as Exhibit 5.1 to the Registration Statement. In giving this consent, we do not thereby admit that we are experts within the meaning of Section 11 of the Securities Act or within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.


Very truly yours,/s/ Mayer Brown LLP