| 1 | M & M Production | | Oil & Gas Operator | Jun 2010 |
| 2 | M & T Petroleum Management Inc | | Oil Operator | May 1984 |
| 3 | M. S. Delone | | Oil Operator | Nov 1990 |
| 4 | Ma-Si, Inc. | | Oil & Gas Operator | May 1998 |
| 5 | Majestic Energy Corporation | Shreveport, LA 71164 | Oil & Gas Operator | May 2013 |
| 6 | Maple Gulf Coast Props. Corp. | | Oil & Gas Operator | Jun 1989 |
| 7 | Marathon Oil Company | Houston, TX 77024 | Oil & Gas Operator | Mar 2024 |
| 8 | Marlin And Davis | | Oil Operator | Sep 1987 |
| 9 | Marshall Exploration, Inc. | | Oil & Gas Operator | Jul 1992 |
| 10 | Martin Production Company | | Oil & Gas Operator | Dec 2023 |
| 11 | Matador Production Company | Dallas, TX 75240 | Oil & Gas Operator | May 2024 |
| 12 | McCormick Production Co, Inc. | Oil City, LA 71061 | Oil & Gas Operator | May 2024 |
| 13 | McGoldrick Oil Company | Shreveport, LA 71129 | Oil & Gas Operator | Jul 2020 |
| 14 | McKenzie Production Company | Houston, TX 77063 | Oil & Gas Operator | May 1995 |
| 15 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 16 | Memorial Production Operating LLC | Houston, TX 77002 | Oil & Gas Operator | May 2024 |
| 17 | Midroc Operating Company | | Oil & Gas Operator | Apr 2013 |
| 18 | Mineral Ventures, Inc. | | Oil & Gas Operator | Dec 2023 |
| 19 | Mississippi River Transm. Corp | | Oil & Gas Operator | Sep 2002 |
| 20 | Mobley Oil Company, Inc. | | Oil & Gas Operator | Feb 1990 |
| 21 | Monroe Well Ser-Oceanyacht1985 | | Oil Operator | Dec 1988 |
| 22 | Monroe Well Ser-Riverside 1985 | | Oil Operator | Dec 1988 |
| 23 | Monroe Well Service-East End | | Oil Operator | Dec 1988 |
| 24 | Monroe Well Service-Sla | | Oil Operator | Mar 1989 |
| 25 | Monsanto Oil Company | | Oil & Gas Operator | Apr 1986 |
| 26 | Moon-Hines-Tigrett Opr Co Inc | | Oil & Gas Operator | Oct 1995 |
| 27 | Moran Oil Co., Inc. | | Oil & Gas Operator | Aug 2009 |
| 28 | Moransco Energy Corporation | Kilgore, TX 75663 | Oil & Gas Operator | May 2024 |
| 29 | Mosbacher Energy Company | Houston, TX 77002 | Oil & Gas Operator | May 2024 |
| 30 | MRD Operating LLC | | Oil & Gas Operator | Dec 2016 |
| 31 | MRT Exploration Co | | Oil & Gas Operator | Feb 1983 |