| 1 | M. W. Maxwell | | Oil & Gas Operator | Apr 1990 |
| 2 | Maddox Oil & Gas | | Gas Operator | Jun 1982 |
| 3 | Mallard Drilling Corp. | | Oil & Gas Operator | Jan 1993 |
| 4 | Marine Properties, Inc. | | Oil & Gas Operator | Feb 1995 |
| 5 | Mark F Preddy & Associates,Inc | | Oil & Gas Operator | Dec 1987 |
| 6 | Marlin Exploration, Inc. | | Oil & Gas Operator | Oct 2006 |
| 7 | Marlin Resources, L.L.C. | Midland, TX 79702 | Oil & Gas Operator | Jan 2025 |
| 8 | Maverick Oil Corp. | | Oil Operator | May 1997 |
| 9 | MBM Partnership | | Gas Operator | Nov 1991 |
| 10 | McBrayer Oil Corporation | Rockport, TX 78381 | Oil & Gas Operator | Nov 1994 |
| 11 | McGoldrick & Watson DRLG., Co. | | Oil & Gas Operator | Jul 1987 |
| 12 | McGoldrick & Watson-Walker | | Oil Operator | Jul 1987 |
| 13 | McGoldrick Oil Company | Shreveport, LA 71129 | Oil & Gas Operator | Jul 2020 |
| 14 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 15 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Oct 2025 |
| 16 | MCZ Oil Co, Inc. | | Oil Operator | Feb 1994 |
| 17 | Meason Operating Company | Natchez, MS 39121 | Oil & Gas Operator | Dec 2011 |
| 18 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 19 | Miles Oil & Gas Co. | | Oil & Gas Operator | Feb 1988 |
| 20 | Milton Galoob | | Oil Operator | Dec 1988 |
| 21 | Miss Lou Oil Producers, Inc. | | Oil & Gas Operator | Dec 1998 |
| 22 | Mobley & Davis | | Oil & Gas Operator | Oct 1986 |
| 23 | Mobley & McCain | | Oil & Gas Operator | Nov 1979 |
| 24 | Monarch Petroleum Corporation | FT Worth, TX 76102 | Oil & Gas Operator | Dec 2019 |
| 25 | Monroe Well Ser-La Petr Assoc | | Oil Operator | Dec 1988 |
| 26 | Monroe Well Service | | Oil & Gas Operator | Apr 1998 |
| 27 | Monroe Well Service-Ajk | | Oil Operator | Dec 1988 |
| 28 | Monroe Well Service-BWK | | Oil Operator | Dec 1988 |
| 29 | Monroe Well Service-Columbus | | Oil Operator | Dec 1988 |
| 30 | Monroe Well Service-East End | | Oil Operator | Dec 1988 |
| 31 | Monroe Well Service-Energy | | Oil Operator | Dec 1988 |
| 32 | Monroe Well Service-Lexington | | Oil Operator | Feb 1989 |
| 33 | Monroe Well Service-Ocean | | Oil Operator | Feb 1989 |
| 34 | Monroe Well Service-Shemen | | Oil Operator | Dec 1988 |
| 35 | Monroe Well Service-Sla | | Oil Operator | Mar 1989 |
| 36 | Monroe Well Service-SPD 1985 | | Oil Operator | Dec 1988 |
| 37 | Monroe Well Service-TBR | | Oil Operator | Aug 1991 |
| 38 | Monroe Well Service-Tpa 1985 | | Oil Operator | Dec 1990 |
| 39 | Monroe Well Service-York | | Oil Operator | Dec 1988 |
| 40 | Moore&Munger Hydrocarbons Inc | | Oil Operator | May 1987 |
| 41 | Munoco Co. | El Dorado, AR 71730 | Oil & Gas Operator | Jul 2021 |
| 42 | Murphrey Oil Co | | Oil Operator | Jan 2025 |