| 1 | M & B Oil Company | Holliday, TX 76366 | Oil & Gas Operator | Feb 2024 |
| 2 | M. H.Marr | | Oil & Gas Operator | Mar 1998 |
| 3 | M. S. Delone | | Oil Operator | Nov 1990 |
| 4 | Ma-Si, Inc. | | Oil & Gas Operator | May 1998 |
| 5 | Marathon Oil Company | Houston, TX 77024 | Oil & Gas Operator | Mar 2024 |
| 6 | Marathon Oil Company/Fina | | Oil & Gas Operator | Jan 2005 |
| 7 | Marlin And Davis | | Oil Operator | Sep 1987 |
| 8 | Marr Company | | Oil & Gas Operator | Mar 1989 |
| 9 | Marshall Exploration, Inc. | | Oil & Gas Operator | Jul 1992 |
| 10 | Maverick Oil Co. | Richland, TX 76681 | Oil Operator | May 2024 |
| 11 | Maverick Producers, Inc. | | Oil Operator | May 2012 |
| 12 | McGoldrick Oil Company | Shreveport, LA 71129 | Oil & Gas Operator | Jul 2020 |
| 13 | McKenzie Petroleum Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 14 | McKenzie Production Company | Houston, TX 77063 | Oil & Gas Operator | May 1995 |
| 15 | McRae Exploration, Inc. | | Oil & Gas Operator | Mar 1984 |
| 16 | McRae Exploration, Inc. & Epm | | Oil & Gas Operator | Mar 1978 |
| 17 | McRae Exploration, Inc. & Herd | | Oil & Gas Operator | Mar 1984 |
| 18 | McRae Exploration,Inc & Bec | | Oil & Gas Operator | Feb 1984 |
| 19 | McRae Oil Corporation | | Oil & Gas Operator | Mar 1984 |
| 20 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 21 | Midroc Operating Company | | Oil & Gas Operator | Apr 2013 |
| 22 | Minatome Corporation | | Oil & Gas Operator | Sep 1987 |
| 23 | Mineral Ventures, Inc. | | Oil & Gas Operator | Dec 2023 |
| 24 | Minerex Engineering Corp. | | Oil & Gas Operator | Mar 2004 |
| 25 | Mobil E&P North America Inc. | | Oil & Gas Operator | Jan 1994 |
| 26 | Mobil Oil E & P Southeast Inc | | Oil & Gas Operator | Sep 2013 |
| 27 | Monroe Well Ser-New American85 | | Oil Operator | Dec 1988 |
| 28 | Monroe Well Serv-New American | | Oil Operator | Dec 1988 |
| 29 | Monroe Well Service | | Oil & Gas Operator | Apr 1998 |
| 30 | Monroe Well Service-Broadway | | Oil Operator | Dec 1988 |
| 31 | Monroe Well Service-Petrol | | Oil Operator | Sep 1992 |
| 32 | Monroe Well Service-Petrovest | | Oil Operator | Dec 1988 |
| 33 | Monroe Well Service-Shemen | | Oil Operator | Dec 1988 |
| 34 | Monterey Resources LLC | Dallas, TX 75230 | Oil & Gas Operator | Oct 2019 |
| 35 | MRD Operating LLC | | Oil & Gas Operator | Dec 2016 |
| 36 | Mrs. C. M. Roberson | | Oil Operator | Mar 1989 |
| 37 | MRT Exploration Co | | Oil & Gas Operator | Feb 1983 |
| 38 | Murphy Exploration & Prod. Co. | Houston, TX 77094 | Oil & Gas Operator | Jun 2011 |
| 39 | Murphy Oil USA Inc | New Orleans, LA 70161 | Oil & Gas Operator | Jan 1993 |