| 1 | Mahoney Drilling | | Gas Operator | Jan 1982 |
| 2 | Mallonee-Mahoney | | Oil & Gas Operator | Dec 1994 |
| 3 | Manuel Corporation | Wichita, KS 67206 | Oil & Gas Operator | Dec 2025 |
| 4 | Marexco | | Oil & Gas Operator | Nov 1994 |
| 5 | Marlin Oil Corporation | Oklahoma City, OK 73113 | Oil & Gas Operator | Nov 2025 |
| 6 | McCoy Petroleum | | Oil & Gas Operator | Aug 1996 |
| 7 | McCoy Petroleum Corporation | Wichita, KS 67207 | Oil & Gas Operator | Dec 2025 |
| 8 | Medicine Bow Operating Company | Houston, TX 77002 | Oil & Gas Operator | Apr 2014 |
| 9 | Merit Energy Company, LLC | Dallas, TX 75009 | Oil & Gas Operator | Sep 2025 |
| 10 | Merrico Resource | | Oil Operator | Dec 1996 |
| 11 | Mesa Operating Co. | Irving, TX 75039 | Oil & Gas Operator | Aug 1997 |
| 12 | Mid Continent Resources, Inc. | Houston, TX 77060 | Oil & Gas Operator | Feb 2026 |
| 13 | Mid-Continent Re | | Oil & Gas Operator | Jan 1993 |
| 14 | Midco Exploration, Inc. | Westmont, IL 60559 | Oil & Gas Operator | Sep 2025 |
| 15 | Midcontinent Acquisition Properties, Inc. | Oklahoma City, OK 73102 | Gas Operator | Jan 2000 |
| 16 | Midwestern Exploration Company | Edmond, OK 73013 | Oil & Gas Operator | May 2025 |
| 17 | Mobil Oil Corpor | | Oil & Gas Operator | Dec 1996 |
| 18 | Mull Drilling Company | Wichita, KS 67206 | Oil & Gas Operator | Nov 2025 |
| 19 | Murfin Drilling | | Oil & Gas Operator | Jul 1997 |
| 20 | Murfin Drilling Company, Inc. | Wichita, KS 67202 | Oil & Gas Operator | Dec 2025 |
| 21 | Mustang Drilling | | Oil & Gas Operator | Nov 1996 |
| 22 | Mustang Oil & Gas Corporation | Wichita Falls, TX 76308 | Oil & Gas Operator | Jul 2021 |
| 23 | MW Oil, Inc | | Oil & Gas Operator | Sep 2025 |