| 101 | Marline Petroleum Corporation | | Oil & Gas Operator | Dec 1985 |
| 102 | Marmaton Oil Company | Houston, TX 77002 | Oil & Gas Operator | Jul 1998 |
| 103 | Maroski, Inc. | | Oil Operator | Jan 1989 |
| 104 | Marquee Corporation | Houston, TX 77024 | Oil & Gas Operator | Apr 2026 |
| 105 | Marquis Resources, LLC | | Oil & Gas Operator | Jul 2021 |
| 106 | Marr Company | | Oil & Gas Operator | Mar 1989 |
| 107 | Marsh Engineering, Inc. | | Oil & Gas Operator | Dec 1990 |
| 108 | Marshall & McCain | | Oil & Gas Operator | Oct 1988 |
| 109 | Marshall Exploration, Inc. | | Oil & Gas Operator | Jun 1992 |
| 110 | Marshall Petroleum, Inc. | Houston, TX 77040 | Oil & Gas Operator | Aug 2003 |
| 111 | Marshall Prod. & Energy Inc. | | Oil & Gas Operator | Jan 1992 |
| 112 | Marshland Exploration Company | | Oil & Gas Operator | May 2006 |
| 113 | Martin Energy LLC | | Oil & Gas Operator | Apr 2023 |
| 114 | Martin Exploration Co. | | Oil & Gas Operator | Apr 1986 |
| 115 | Martin Oil & Gas Co. | | Oil Operator | Jul 1981 |
| 116 | Martin Oil Co. | Aspermont, TX 79502 | Oil & Gas Operator | Jul 2023 |
| 117 | Martin Production Company | | Oil & Gas Operator | Dec 2024 |
| 118 | Martin-Marks Operating Co. LLC | | Oil & Gas Operator | Dec 2010 |
| 119 | Martineau Petroleum, Inc. | Dallas, TX 75206 | Oil & Gas Operator | Jan 2025 |
| 120 | Marvin L. Muslow | | Oil Operator | Jun 1995 |
| 121 | Mass Resources, Inc. | | Oil Operator | Jan 2025 |
| 122 | Master Well Works, Inc. | | Oil Operator | Dec 2024 |
| 123 | Masters Resources, L.L.C. | Houston, TX 77079 | Oil & Gas Operator | Dec 2008 |
| 124 | Matador Operating Company | Dallas, TX 75240 | Oil & Gas Operator | Jul 2003 |
| 125 | Matador Production Company | Dallas, TX 75240 | Oil & Gas Operator | Apr 2026 |
| 126 | Matrix Oil & Gas, Inc. | | Oil & Gas Operator | Jul 2001 |
| 127 | Matrix Production Company | Sugar Land, TX 77478 | Oil & Gas Operator | Feb 2026 |
| 128 | Matthews Operating Co., Inc. | | Gas Operator | Aug 2001 |
| 129 | Matzinger & Bell Inc-Carl O&G | | Oil & Gas Operator | Dec 1981 |
| 130 | Matzinger & Bell, Inc. | | Oil & Gas Operator | Dec 1982 |
| 131 | Matzinger Petroleum Co. | | Oil & Gas Operator | Jan 1991 |
| 132 | Maurine B. Pyle | | Oil & Gas Operator | Mar 1993 |
| 133 | Maverick Oil Co. | Richland, TX 76681 | Oil Operator | Apr 2026 |
| 134 | Maverick Oil Corp. | | Oil Operator | May 1997 |
| 135 | Maverick Producers, Inc. | | Oil Operator | May 2012 |
| 136 | Maxim Energy Corporation | Baytown, TX 77520 | Oil & Gas Operator | Feb 2026 |
| 137 | Maximus Operating, LTD. | Kilgore, TX 75663 | Oil & Gas Operator | Apr 2026 |
| 138 | Maxum Energy Corp | Plano, TX 75025 | Oil & Gas Operator | Jan 2003 |
| 139 | Maxus Exploration Company | Dallas, TX 75201 | Oil & Gas Operator | Jan 1995 |
| 140 | Maxwell Oil & Gas Corp. | Kilgore, TX 75663 | Oil & Gas Operator | Jan 2001 |
| 141 | May Oil & Gas, L.L.C. | | Oil & Gas Operator | Dec 2013 |
| 142 | May Petroleum Inc | Dallas, TX 75231 | Oil & Gas Operator | Nov 1998 |
| 143 | Maybrier Brothers | | Oil Operator | Apr 2006 |
| 144 | Maybrier Production, L.L.C. | | Oil Operator | Oct 2022 |
| 145 | Maynard Oil Co. | Denver, CO 80202 | Oil & Gas Operator | Sep 2004 |
| 146 | Mayne & Mertz, Inc. | Midland, TX 79702 | Oil & Gas Operator | Mar 2013 |
| 147 | MBM Partnership | | Gas Operator | Nov 1991 |
| 148 | Mbo, LLC | | Oil Operator | Jan 2025 |
| 149 | McAlester Fuel Co. | Houston, TX 77042 | Oil & Gas Operator | Jan 2010 |
| 150 | McBrayer Oil Corporation | Rockport, TX 78381 | Oil & Gas Operator | Nov 1994 |
| 151 | McCarter-Greenbrier-Macdonald | | Oil Operator | Sep 1981 |
| 152 | McClinton & 4-M Invest Inc | | Oil & Gas Operator | Aug 1992 |
| 153 | McClinton & Mosing | | Oil & Gas Operator | Oct 1977 |
| 154 | McConathy & Associates | | Oil & Gas Operator | Dec 1983 |
| 155 | McConathy Production Co.,Inc. | | Oil & Gas Operator | Jun 1990 |
| 156 | McCord Exploration Co. | | Oil & Gas Operator | Dec 1990 |
| 157 | McCord Oil Co. And T. Walker | | Oil & Gas Operator | Dec 1985 |
| 158 | McCord-Dale Exploration | | Oil & Gas Operator | May 1986 |
| 159 | McCord-Goodrich Oil Company | | Oil & Gas Operator | Oct 1991 |
| 160 | McCormick Operating Company | | Oil & Gas Operator | Mar 1984 |
| 161 | McCormick Operating PRTNSHP | | Oil & Gas Operator | Sep 1985 |
| 162 | McCormick Production Co, Inc. | Oil City, LA 71061 | Oil & Gas Operator | Apr 2026 |
| 163 | McCormick-Bintliff | | Oil & Gas Operator | Feb 1984 |
| 164 | McCormick-Bintliff-Pettit | | Oil & Gas Operator | Feb 1984 |
| 165 | McCormick-Ciroco, Inc. | | Oil & Gas Operator | Jan 1984 |
| 166 | McCormick-Terra-Bintliff | | Oil & Gas Operator | Dec 1979 |
| 167 | McCormick-WHB | | Gas Operator | Jan 1984 |
| 168 | McCulloch Oil Corp.-Ids | | Oil & Gas Operator | Dec 1981 |
| 169 | McCurdy Oil Co. | Fort Worth, TX 76116 | Oil & Gas Operator | Jan 2025 |
| 170 | McDaniel Petroleum Company, Inc. | | Oil Operator | Jun 2020 |
| 171 | McDowell And Cook, Inc. | | Oil Operator | Jan 1987 |
| 172 | McElroy Drilling Co., Inc. | | Gas Operator | Dec 1987 |
| 173 | McFarland Energy, Inc. | New Orleans, LA 70160 | Oil & Gas Operator | Dec 2009 |
| 174 | McGoldrick & Watson | | Oil & Gas Operator | Jul 1987 |
| 175 | McGoldrick & Watson - Alagood | | Oil Operator | Oct 1995 |
| 176 | McGoldrick & Watson DRLG., Co. | | Oil & Gas Operator | Jul 1987 |
| 177 | McGoldrick & Watson, Et Al | | Oil Operator | Jul 1987 |
| 178 | McGoldrick & Watson-Walker | | Oil Operator | Jul 1987 |
| 179 | McGoldrick Oil Company | Shreveport, LA 71129 | Oil & Gas Operator | Jul 2020 |
| 180 | McGowan Working Partners | Jackson, MS 39296 | Oil & Gas Operator | Dec 2000 |
| 181 | McGowan Working Partners, Inc. | Jackson, MS 39296 | Oil & Gas Operator | Apr 2026 |
| 182 | McGowen Resources Co., Inc. | Dallas, TX 75206 | Oil & Gas Operator | Aug 2003 |
| 183 | McIlhenny-Powell Operating Co | | Gas Operator | Aug 1983 |
| 184 | McIntyre Oil Company | | Oil & Gas Operator | Jan 1992 |
| 185 | McKenzie Management Inc. | | Oil & Gas Operator | Aug 1989 |
| 186 | McKenzie Petroleum Company | Houston, TX 77063 | Oil & Gas Operator | Aug 1995 |
| 187 | McKenzie Production Company | Houston, TX 77063 | Oil & Gas Operator | May 1995 |
| 188 | McLain J. Forman | | Oil & Gas Operator | Mar 1988 |
| 189 | McLaurin Oil Co. | | Oil Operator | Jan 2025 |
| 190 | McLeod Gas Gath & Proc Co. L.L.C. | | Oil Operator | Jul 2012 |
| 191 | McMoran Exploration Company | | Oil & Gas Operator | May 1985 |
| 192 | McMoran Oil & Gas LLC | New Orleans, LA 70160 | Oil & Gas Operator | Oct 2021 |
| 193 | McMoran Production Co. | | Oil & Gas Operator | May 1985 |
| 194 | McMoran-Transco | | Oil & Gas Operator | Aug 1979 |
| 195 | McMullan Oil Company | San Antonio, TX 78212 | Oil & Gas Operator | Jun 2023 |
| 196 | McOr Oil & Gas Corp | Houston, TX 77002 | Oil & Gas Operator | Oct 2013 |
| 197 | McOr Oil Development, Inc. | | Oil & Gas Operator | Feb 1990 |
| 198 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 199 | McRae Exploration, Inc. | | Oil & Gas Operator | Mar 1984 |
| 200 | McRae Exploration, Inc. & Epm | | Oil & Gas Operator | Mar 1978 |