EXHIBIT 32.1

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350

     In connection with the Annual Report of Ultra Petroleum Corp. (the “Company”) on Form 10-K for the fiscal year ended December 31, 2005, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Michael D. Watford, President and Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to my knowledge:

     (1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

     (2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of, and for the periods presented in the Report.

Dated: March 31, 2006

/s/ Michael D. Watford  

Michael D. Watford, Chief Executive Officer 

CERTIFICATION PURSUANT TO
18 U.S.C. SECTION 1350

     In connection with the Annual Report of Ultra Petroleum Corp. (the “Company”) on Form 10-K for the fiscal year ended December 31, 2005, as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Marshall D. Smith, Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to my knowledge:

     (1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended; and

     (2) The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company as of, and for the periods presented in the Report.

Dated: March 31, 2006

/s/ Marshall D. Smith  

Marshall D. Smith, Chief Financial Officer 

The foregoing certifications are being furnished as an exhibit to the Report pursuant to Item 601(b)(32) of Regulation S-K and Section 906 of the Sarbanes-Oxley Act of 2002 (subsections (a) and (b) of Section 1350, Chapter 63 of Title 18, United States Code) and, accordingly, are not being filed as part of the Report for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, and are not incorporated by reference into any filing of the Company, whether made before or after the date hereof, regardless of any general incorporation language in such filing.