| 1 | M & B Oil Company | Holliday, TX 76366 | Oil & Gas Operator | Nov 2025 |
| 2 | M2 Louisiana Gas Service, LLC | | Oil Operator | Apr 2010 |
| 3 | Magnum Gas Pipeline, L.L.C. | | Oil Operator | Dec 2024 |
| 4 | Mallard Drilling Corp. | | Oil & Gas Operator | Jan 1993 |
| 5 | Mallard DRLG & Central Oil Co | | Gas Operator | Mar 1978 |
| 6 | Maple Gulf Coast Props. Corp. | | Oil & Gas Operator | Jun 1989 |
| 7 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Dec 2025 |
| 8 | Marlan Anderson | | Oil Operator | Jan 2025 |
| 9 | Marlin Exploration, LLC | | Oil & Gas Operator | Nov 2025 |
| 10 | Maroski, Inc. | | Oil Operator | Jan 1989 |
| 11 | Marshall Exploration, Inc. | | Oil & Gas Operator | Jun 1992 |
| 12 | Martin Production Company | | Oil & Gas Operator | Dec 2024 |
| 13 | Martineau Petroleum, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Jan 2025 |
| 14 | Matador Production Company | Dallas, TX 75240 | Oil & Gas Operator | Feb 2026 |
| 15 | Matthews Operating Co., Inc. | | Gas Operator | Aug 2001 |
| 16 | Maximus Operating, LTD. | Kilgore, TX 75663 | Oil & Gas Operator | Feb 2026 |
| 17 | May Petroleum Inc | Dallas, TX 75231 | Oil & Gas Operator | Nov 1998 |
| 18 | McCulloch Oil Corporation | | Oil & Gas Operator | Feb 1978 |
| 19 | McGoldrick Oil Company | Shreveport, LA 71129 | Oil & Gas Operator | Jul 2020 |
| 20 | McIlhenny-Powell Operating Co | | Gas Operator | Aug 1983 |
| 21 | Memorial Production Operating LLC | Houston, TX 77002 | Oil & Gas Operator | Feb 2026 |
| 22 | Mettz,Carmody & Foster Oil Co | | Oil Operator | May 1990 |
| 23 | Mich-La Oil & Gas Exploration | | Oil & Gas Operator | Jan 1992 |
| 24 | Mid South Oil & Gas Expl Inc | | Oil & Gas Operator | Jan 1992 |
| 25 | Mid-Con Energy Operating, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | May 2020 |
| 26 | Mid-Con Energy Operating, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Dec 2025 |
| 27 | Mike Revere | | Oil & Gas Operator | Jul 1991 |
| 28 | Mineral Development, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Aug 1996 |
| 29 | Mobley Valve Service, Inc. | | Oil & Gas Operator | Nov 2006 |
| 30 | Monroe Well Service-Petrovest | | Oil Operator | Dec 1988 |
| 31 | Monte Carlo Exploration Inc. | | Oil & Gas Operator | Oct 1984 |
| 32 | Mooringsport Energy Prod Corp | | Oil & Gas Operator | Oct 1994 |
| 33 | Moran Oil Co., Inc. | | Oil & Gas Operator | Aug 2009 |
| 34 | Moransco Energy Corporation | Kilgore, TX 75663 | Oil & Gas Operator | Feb 2026 |
| 35 | MRD Operating LLC | | Oil & Gas Operator | Dec 2016 |