| 1 | M & B Oil Company | Holliday, TX 76366 | Oil & Gas Operator | Dec 2025 |
| 2 | M & J Operator | | Oil & Gas Operator | May 2026 |
| 3 | M & T Oil Company | Copan, OK 74022 | Oil Operator | Dec 2025 |
| 4 | M. D. & G. Partnership | | Oil & Gas Operator | Dec 1996 |
| 5 | M. H. Whittier Energy LLC | | Oil & Gas Operator | Sep 1996 |
| 6 | Macpherson Oil Company LLC | | Oil & Gas Operator | May 2026 |
| 7 | Macpherson Operating Company L.P. | | Oil & Gas Operator | May 2026 |
| 8 | Magness Petroleum Company | | Oil & Gas Operator | Dec 1994 |
| 9 | Manley Energy Resources LLC | | Oil Operator | Jan 2018 |
| 10 | Maranatha Petroleum Inc. | | Oil & Gas Operator | Dec 2025 |
| 11 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | May 2026 |
| 12 | Marathon Oil Company Operator | | Oil & Gas Operator | Dec 1993 |
| 13 | Maria L. Andrade | | Oil Operator | Dec 2006 |
| 14 | Marina Pacifica Oil Company | | Oil & Gas Operator | Dec 1981 |
| 15 | Mariposa Petroleum Co. | | Gas Operator | Dec 1980 |
| 16 | Marlin Pacific Oil & Gas | | Oil & Gas Operator | Dec 2003 |
| 17 | Marlyn Company | | Oil & Gas Operator | Dec 2009 |
| 18 | Marmac Resources Company | | Oil & Gas Operator | Mar 2015 |
| 19 | Mary E. Wertalla | | Oil Operator | Dec 1984 |
| 20 | Matrix Oil Corporation | | Oil & Gas Operator | May 2026 |
| 21 | Mauro J. Dentino | | Oil Operator | Dec 2025 |
| 22 | Maxim Resources LTD U.S.A. | | Oil & Gas Operator | Dec 1997 |
| 23 | Maxoil Inc. | | Oil & Gas Operator | Dec 2004 |
| 24 | Maxus Exploration Company | Dallas, TX 75201 | Oil & Gas Operator | Jan 1995 |
| 25 | Maya Oil LLC | | Oil Operator | May 2026 |
| 26 | McBo Oil Co. | | Oil & Gas Operator | Dec 1996 |
| 27 | McDonald Ranch Partnership | | Oil Operator | Dec 2025 |
| 28 | McFarland Energy, Inc. | New Orleans, LA 70160 | Oil & Gas Operator | Dec 2009 |
| 29 | McKean Bros. | | Oil & Gas Operator | Dec 1997 |
| 30 | McKenzie & Assoc. | | Gas Operator | Dec 1990 |
| 31 | McLennan Family Properties L.P. | | Oil & Gas Operator | Dec 2021 |
| 32 | McOr Oil & Gas Corp | Houston, TX 77002 | Oil & Gas Operator | Oct 2013 |
| 33 | Medallion Calif Properties Co. | | Oil & Gas Operator | Dec 2003 |
| 34 | Mendell Davis Gas Partners LLC | | Oil & Gas Operator | Dec 2013 |
| 35 | Mentren Corporation | | Gas Operator | May 2026 |
| 36 | Meritage Homes Of California Inc. | | Oil Operator | Dec 2020 |
| 37 | Midway-Sunset Investors LLC | | Oil & Gas Operator | May 2026 |
| 38 | Mills Oil Co. | | Oil Operator | Dec 1986 |
| 39 | Mission Oil Company | | Oil & Gas Operator | Apr 2026 |
| 40 | Mission Resources | | Oil & Gas Operator | Dec 1991 |
| 41 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 42 | Mitchell Oil | | Oil Operator | Dec 2025 |
| 43 | Mitchell-Grossu Oil Co. | | Oil & Gas Operator | Sep 2023 |
| 44 | Mitchwil Investments LLC | | Oil & Gas Operator | Dec 2019 |
| 45 | Mobil Oil Corporation | Houston, TX 77210 | Oil & Gas Operator | Dec 2007 |
| 46 | Mobil Oil Exploration & Production North America Inc. | | Oil & Gas Operator | Dec 1996 |
| 47 | Modus Inc. | | Oil & Gas Operator | May 2026 |
| 48 | Monterey Resources Inc. | | Oil & Gas Operator | Dec 1997 |
| 49 | Monument Production Inc. | | Oil & Gas Operator | Dec 2011 |
| 50 | Morrison Oil Co. LLC | | Oil & Gas Operator | Apr 2026 |
| 51 | Morton And Dolley | | Oil Operator | Dec 1991 |
| 52 | Mountain VIew Resources LLC | | Oil & Gas Operator | May 2026 |
| 53 | Murray-Teague Assoc. | | Oil Operator | Dec 2005 |
| 54 | Mutz Oil Operator | | Oil Operator | Dec 1988 |