| 101 | Contango Rocky Mountain Inc | Houston, TX 77002 | Oil & Gas Operator | Jan 2020 |
| 102 | Continental Industries LC | Casper, WY 82602 | Oil & Gas Operator | Feb 2008 |
| 103 | Continental Operating Co. | Houston, TX 77024 | Oil & Gas Operator | Oct 2025 |
| 104 | Continental Production Co LLC | Greenwood VIllage, CO 80155 | Oil & Gas Operator | Aug 2012 |
| 105 | Continental Resources, Inc. | Oklahoma City, OK 73126 | Oil & Gas Operator | Oct 2025 |
| 106 | Convest Energy Corporation | Houston, TX 77057 | Oil & Gas Operator | Sep 2014 |
| 107 | Cook D L | Holliday, TX 76366 | Oil & Gas Operator | Dec 2008 |
| 108 | Coquina Oil Corporation | Houston, TX 77227 | Oil & Gas Operator | Mar 2015 |
| 109 | Coral Production Corporation | Denver, CO 80201 | Oil & Gas Operator | Jun 2025 |
| 110 | Cordero Mining Co | Gillette, WY 82717 | Oil Operator | Nov 2009 |
| 111 | Cordero Oil And Gas LLC | Gillette, WY 82716 | Oil Operator | Nov 2021 |
| 112 | Cordillera Corporation | Denver, CO 80237 | Oil & Gas Operator | Feb 1996 |
| 113 | Cork Petroleum Corporation | Thermopolis, WY 82443 | Oil & Gas Operator | Apr 2012 |
| 114 | Cornerstone Natural Resources LLC | Denver, CO 80234 | Oil & Gas Operator | Aug 2025 |
| 115 | Coronado Oil Company | Denver, CO 80202 | Oil & Gas Operator | Dec 2019 |
| 116 | Corrida Oil Inc | Denver, CO 80217 | Oil & Gas Operator | Jun 1990 |
| 117 | Costilla Energy Inc | Midland, TX 79702 | Oil & Gas Operator | Mar 2008 |
| 118 | Cotton Petroleum Corporation | Tulsa, OK 74102 | Oil & Gas Operator | Jan 2005 |
| 119 | Cottonwood Oil Inc | Worland, WY 82401 | Oil & Gas Operator | Jun 1988 |
| 120 | Cowan Oil Company | | Oil Operator | Sep 1990 |
| 121 | Cowboy Clean Fuels LLC | Laramie, WY 82072 | Gas Operator | Jul 2025 |
| 122 | Cox Edwin L & Berry R | | Oil & Gas Operator | Oct 1987 |
| 123 | Cox Kendall Jay | Recluse, WY 28775 | Oil & Gas Operator | Aug 2016 |
| 124 | CR Energy | | Oil & Gas Operator | Dec 1992 |
| 125 | Cramer Oil Company | Denver, CO 80202 | Oil Operator | Aug 2012 |
| 126 | Crawley Petroleum Corporation | Oklahoma City, OK 73102 | Oil & Gas Operator | Oct 2025 |
| 127 | Creek Oil Company | Colorado Springs, CO 80906 | Oil & Gas Operator | Aug 2001 |
| 128 | Crest Resources Inc | Tulsa, OK 74103 | Oil & Gas Operator | Oct 2025 |
| 129 | Crowheart Energy LLC | Baggs, WY 82321 | Oil & Gas Operator | Jul 2025 |
| 130 | Crown Central Petroleum Corp | Richmond, TX 77469 | Oil & Gas Operator | Dec 1999 |
| 131 | Crown Energy Partners LLC | Englewood, CO 80112 | Oil & Gas Operator | Sep 2013 |
| 132 | Crown Oil & Gas Co Inc | Labarge, WY 83123 | Oil & Gas Operator | Jan 2023 |
| 133 | Crystal Exploration & Production Company | Shreveport, LA 71120 | Oil & Gas Operator | Feb 1995 |
| 134 | Crystal Oil Company | Shreveport, LA 71120 | Oil & Gas Operator | Jul 1995 |
| 135 | Cumberland Operating LLC | Cody, WY 82414 | Oil & Gas Operator | Aug 2025 |
| 136 | Czar Resources Inc | Houston, TX 77060 | Oil & Gas Operator | Oct 1992 |