| 201 | McMullan Oil Company | San Antonio, TX 78212 | Oil & Gas Operator | Jun 2023 |
| 202 | McOr Oil & Gas Corp | Houston, TX 77002 | Oil & Gas Operator | Oct 2013 |
| 203 | McOr Oil Development, Inc. | | Oil & Gas Operator | Feb 1990 |
| 204 | McRae Exploration & Prod., Inc. | Houston, TX 77064 | Oil & Gas Operator | Feb 2017 |
| 205 | McRae Exploration, Inc. | | Oil & Gas Operator | Mar 1984 |
| 206 | McRae Exploration, Inc. & Epm | | Oil & Gas Operator | Mar 1978 |
| 207 | McRae Exploration, Inc. & Herd | | Oil & Gas Operator | Mar 1984 |
| 208 | McRae Exploration,Inc & Bec | | Oil & Gas Operator | Feb 1984 |
| 209 | McRae Oil Corporation | | Oil & Gas Operator | Mar 1984 |
| 210 | MCZ Oil Co, Inc. | | Oil Operator | Feb 1994 |
| 211 | MCZ, Inc. | Houston, TX 77026 | Oil & Gas Operator | Sep 1990 |
| 212 | Meason Operating Company | Natchez, MS 39121 | Oil & Gas Operator | Dec 2011 |
| 213 | Mec-Goodrich Oil Co. | | Oil & Gas Operator | Feb 1985 |
| 214 | Medallion Petroleum, Inc. | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2015 |
| 215 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 216 | Medders Oil Company | Wichita Falls, TX 76308 | Oil & Gas Operator | Mar 2025 |
| 217 | Mega Drilling Company | | Oil Operator | Feb 1984 |
| 218 | Melren Oil & Gas Expl., Inc. | | Gas Operator | Nov 1989 |
| 219 | Memaca Petroleum Corporation | | Oil & Gas Operator | Jan 1990 |
| 220 | Memorial Exploration Company | Saint Louis, MO 63105 | Oil & Gas Operator | Aug 1996 |
| 221 | Memorial Production Operating LLC | Houston, TX 77002 | Oil & Gas Operator | Mar 2025 |
| 222 | Meng Oper. & Expl. Co. | | Oil & Gas Operator | Dec 1989 |
| 223 | Menoah Petroleum Inc | | Oil & Gas Operator | Dec 2024 |
| 224 | Meridian Oil Inc. | Houston, TX 77210 | Oil & Gas Operator | Aug 1996 |
| 225 | Meridian Oil Offshore Inc. | | Oil & Gas Operator | Aug 1996 |
| 226 | Meridian Resources USA Inc | | Oil & Gas Operator | Aug 2024 |
| 227 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Mar 2025 |
| 228 | Merl Wiggins Et Al | | Oil & Gas Operator | Sep 1996 |
| 229 | Merlin J Verret | | Gas Operator | Jun 1986 |
| 230 | Merrico Resources, Inc. | Ardmore, OK 73402 | Oil & Gas Operator | Mar 2008 |
| 231 | Merritt Operating, Inc. | Mineola, TX 75773 | Oil & Gas Operator | Mar 2025 |
| 232 | Mertz Energy LLC | Houston, TX 77098 | Oil & Gas Operator | Jan 2025 |
| 233 | Mesa Gulf Coast LLC | | Oil & Gas Operator | Dec 2020 |
| 234 | Mesa Operating LTD Partnership | Amarillo, TX 79189 | Oil & Gas Operator | May 1994 |
| 235 | Mesa Petroleum Co. | | Oil & Gas Operator | Aug 1985 |
| 236 | Mescalero Energy, Inc. | San Antonio, TX 78231 | Oil & Gas Operator | Aug 2003 |
| 237 | Metairie Energy Company, Inc. | | Oil & Gas Operator | Nov 2019 |
| 238 | Metro Energy Group, Inc. | Bossier City, LA 71112 | Oil & Gas Operator | May 2013 |
| 239 | Mettz,Carmody & Foster Oil Co | | Oil Operator | May 1990 |
| 240 | Meyers-Lasher, Inc. | | Oil & Gas Operator | Mar 1999 |
| 241 | MFP Petroleum LTD. Partnership | Oklahoma City, OK 73142 | Oil & Gas Operator | Nov 2017 |
| 242 | MGF Oil Corporation | Tulsa, OK 74121 | Oil & Gas Operator | Jun 1998 |
| 243 | Mich-La Oil & Gas Exploration | | Oil & Gas Operator | Jan 1992 |
| 244 | Michael D Brown | | Oil Operator | Jul 1993 |
| 245 | Michael W Mills | | Oil Operator | Jul 2007 |
| 246 | Michel T. Halbouty | | Oil & Gas Operator | Dec 1996 |
| 247 | Michel T. Halbouty Energy Co. | | Oil & Gas Operator | Nov 1986 |
| 248 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 249 | Micron Minerals Company | | Oil & Gas Operator | Sep 1988 |
| 250 | Mid Field Oil Co. | | Oil & Gas Operator | Mar 1989 |
| 251 | Mid Louisiana Gas Company | | Oil & Gas Operator | Oct 2002 |
| 252 | Mid South Oil & Gas Expl Inc | | Oil & Gas Operator | Jan 1992 |
| 253 | Mid-America Resources Corporation | | Oil Operator | Jan 2019 |
| 254 | Mid-America Resources, Inc. | | Oil & Gas Operator | Feb 2008 |
| 255 | Mid-America/Hughes & Hughes | | Oil Operator | Jul 1984 |
| 256 | Mid-Con Energy Operating, Inc. | Tulsa, OK 74136 | Oil & Gas Operator | May 2020 |
| 257 | Mid-Con Energy Operating, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Feb 2025 |
| 258 | Mid-Continent Energy Operating | | Gas Operator | Aug 2007 |
| 259 | Mid-Continent Energy, Inc. | Tulsa, OK 74103 | Oil & Gas Operator | Apr 2020 |
| 260 | Mid-National Resources Inc. | | Oil Operator | Feb 1999 |
| 261 | Mid-South Trading, Inc. | | Oil & Gas Operator | Jan 2025 |
| 262 | Middle Bay Oil Company, Inc. | Houston, TX 77002 | Oil & Gas Operator | Apr 1998 |
| 263 | Middle Bay Production Co. Inc. | Houston, TX 77010 | Oil & Gas Operator | Sep 2014 |
| 264 | Mideast Gas Systems, Inc. | Midland, TX 79702 | Oil & Gas Operator | Dec 2005 |
| 265 | Midla, LTD. | | Oil & Gas Operator | Jun 1990 |
| 266 | Midland Workover, Inc. | | Oil & Gas Operator | Dec 2024 |
| 267 | Midnight Drilling LLC | | Oil & Gas Operator | Jan 2016 |
| 268 | Midroc Operating Company | | Oil & Gas Operator | Apr 2013 |
| 269 | Midstates Oil Company | Oklahoma City, OK 73112 | Oil & Gas Operator | Nov 2000 |
| 270 | Midstates Petroleum Company LLC | Tulsa, OK 74103 | Oil & Gas Operator | May 2018 |
| 271 | Midstates Petroleum Corp. | | Oil & Gas Operator | Dec 2008 |
| 272 | Midway Production Co. | | Gas Operator | May 1990 |
| 273 | Midway Testing Company Inc | | Gas Operator | Mar 1984 |
| 274 | Midwest Energy Companies, Inc. | | Oil & Gas Operator | Feb 1998 |
| 275 | Midwest Enterprises, Inc. | Cashion, OK 73016-9626 | Oil & Gas Operator | Oct 2024 |
| 276 | Mike Bonner | | Oil Operator | Aug 1999 |
| 277 | Mil-Cro Inc. | | Oil Operator | Jan 1994 |
| 278 | Milagro Exploration, LLC | Houston, TX 77010 | Oil & Gas Operator | Aug 2018 |
| 279 | Miles Oil & Gas Co. | | Oil & Gas Operator | Feb 1988 |
| 280 | Millennium Offshore Group, Inc. | Houston, TX 77007 | Oil & Gas Operator | Sep 2005 |
| 281 | Miller Exploration Company | Tulsa, OK 74136-1020 | Oil & Gas Operator | Mar 2015 |
| 282 | Miller Oil Field Services, Inc | | Oil Operator | Feb 1990 |
| 283 | Miller S.W.D., Inc. | | Oil Operator | Oct 2002 |
| 284 | Milton Crow,Inc.&RP Evans Etal | | Oil & Gas Operator | Aug 1988 |
| 285 | Milton Galoob | | Oil Operator | Dec 1988 |
| 286 | Minatome Corpora | | Oil & Gas Operator | Sep 1987 |
| 287 | Minden Oil & Gas, Inc. | | Oil & Gas Operator | May 1985 |
| 288 | Mineral Development, Inc. | Dallas, TX 75231 | Oil & Gas Operator | Aug 1996 |
| 289 | Mineral Ventures, Inc. | | Oil & Gas Operator | Dec 2024 |
| 290 | Minerex Engineering Corp. | | Oil & Gas Operator | Mar 2004 |
| 291 | Miocene Oil & Gas, LTD. | Englewood, CO 80110 | Oil & Gas Operator | Mar 2025 |
| 292 | Miss Chub LLC | | Gas Operator | Dec 2024 |
| 293 | Miss Lou Oil Producers, Inc. | | Oil & Gas Operator | Dec 1998 |
| 294 | Miss-Lou Operating, LLC | | Oil & Gas Operator | Dec 2024 |
| 295 | Miss-Lou Petroleum LLC | | Oil & Gas Operator | Jun 2011 |
| 296 | Mission Energy Inc. | Midland, TX 79702 | Oil & Gas Operator | Mar 2025 |
| 297 | Mission Exploration, Inc. | Tolar, TX 76476 | Oil & Gas Operator | Dec 1987 |
| 298 | Mission Resources Corporation | Houston, TX 77002 | Oil & Gas Operator | Mar 2008 |
| 299 | Mission River Systems, Inc. | Corpus Chrsti, TX 78473 | Oil & Gas Operator | Mar 2025 |
| 300 | Mississippi River Transm. Corp | | Oil & Gas Operator | Sep 2002 |