| 401 | Map Oil Co. | | Oil Operator | Jan 1978 |
| 402 | Map Production Co., Inc. | Kilgore, TX 75663 | Oil & Gas Operator | Feb 2026 |
| 403 | Mapco Inc | Billings, MT 59102 | Oil & Gas Operator | Dec 1983 |
| 404 | Mapco Oil & Gas Company | Tulsa, OK 74101-2115 | Oil & Gas Operator | Jan 1985 |
| 405 | Mapco Oil Company | | Oil & Gas Operator | Jan 1985 |
| 406 | Mapco Prod Compa | | Gas Operator | Dec 1984 |
| 407 | Mapco Production Co | Billings, MT 59102 | Oil & Gas Operator | Apr 1994 |
| 408 | Maple Energy Holdings, LLC | Houston, TX 77007 | Oil & Gas Operator | Sep 2023 |
| 409 | Maple Grove Enterprises Inc | Rimersburg, PA 16248-6415 | Oil & Gas Operator | Dec 2025 |
| 410 | Maple Gulf Coast Props. Corp. | | Oil & Gas Operator | Jun 1989 |
| 411 | Maple Lane Farms Dairy And Grain LLC | Marietta, NY 13110 | Gas Operator | Dec 2024 |
| 412 | Maple Leaf Energ | | Oil & Gas Operator | Sep 1989 |
| 413 | Maple Properties Corp | Dallas, TX 75204 | Oil & Gas Operator | Jan 1999 |
| 414 | Mapleton Gas Pipeline, Inc. | Mapleton, KS 66754 | Gas Operator | Jun 2011 |
| 415 | Mar Oil & Gas Corp. | Santa Fe, NM 87502 | Oil & Gas Operator | Dec 2025 |
| 416 | Mar Oil Company | Upper Sandusky, OH 43351 | Oil & Gas Operator | Dec 2023 |
| 417 | Mar-Bar Enterprises Inc | Cushing, OK 74023-3031 | Oil Operator | Nov 2025 |
| 418 | Mar-Bec Energy Company, L.L.C. | Shreveport, LA 71105 | Oil & Gas Operator | May 2001 |
| 419 | Mar-Lou Oil Co., LLC | Wilson, KS 67490 | Oil Operator | Sep 2025 |
| 420 | Mar-Low Corporation | | Oil & Gas Operator | Mar 1992 |
| 421 | Mar-Win Development Co. | | Oil & Gas Operator | Nov 1988 |
| 422 | Mar/Reg Investments | Irving, TX 75016 | Oil & Gas Operator | Jul 1999 |
| 423 | Mar/Reg Oil Company | Reno, NV 89511 | Oil & Gas Operator | Dec 2025 |
| 424 | Maralex Resources Inc | Ignacio, CO 81137 | Oil & Gas Operator | Dec 2025 |
| 425 | Maralo, Inc. | Midland, TX 79702 | Oil & Gas Operator | Dec 1998 |
| 426 | Maralo, LLC | Midland, TX 79702 | Oil & Gas Operator | Mar 2008 |
| 427 | Maram Energy Inc | MT Vernon, OH 43050 | Oil & Gas Operator | Dec 2024 |
| 428 | Maran Oil Company | San Antonio, TX 78216 | Oil & Gas Operator | Dec 2020 |
| 429 | Maran Oil Company, LLC | San Antonio, TX 78216 | Oil & Gas Operator | Mar 2022 |
| 430 | Maranatha Energy Corporation | Athens, WV 24712 | Oil & Gas Operator | Dec 2021 |
| 431 | Maranatha Exploration Inc | Killbuck, OH 44637 | Oil & Gas Operator | Dec 1992 |
| 432 | Maranatha Exploration, LP | Wichita Falls, TX 76307 | Oil Operator | Feb 2012 |
| 433 | Maranatha Oil Company | Gonzales, TX 78629 | Oil & Gas Operator | Feb 2026 |
| 434 | Maranatha Petroleum Inc. | | Oil & Gas Operator | Nov 2025 |
| 435 | Marata Oil & Gas Company | Dallas, TX 75225 | Oil & Gas Operator | Aug 2003 |
| 436 | Marathon Corporation | | Oil Operator | Dec 1994 |
| 437 | Marathon Oil Co.-Rocky Mountain Region | Cody, WY 82414 | Oil Operator | Dec 1999 |
| 438 | Marathon Oil Com | | Oil & Gas Operator | Dec 1996 |
| 439 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Dec 2025 |
| 440 | Marathon Oil Company LLC | Houston, TX 77079 | Oil & Gas Operator | Dec 2025 |
| 441 | Marathon Oil Company Operator | | Oil & Gas Operator | Dec 1993 |
| 442 | Marathon Oil Company/Fina | | Oil & Gas Operator | Jan 2005 |
| 443 | Marathon Oil Ef LLC | Houston, TX 77252 | Oil & Gas Operator | Feb 2026 |
| 444 | Marathon Oil Permian LLC | Midland, TX 79701 | Oil & Gas Operator | Dec 2025 |
| 445 | Marben Corporation | | Oil Operator | Jul 1995 |
| 446 | Marbet LLC | Edmond, OK 73013-6691 | Oil & Gas Operator | Dec 2025 |
| 447 | Marbil Oil, Inc. | Olney, TX 76374 | Oil & Gas Operator | Jun 2013 |
| 448 | Marbill Drilling Company | | Gas Operator | Dec 2001 |
| 449 | Marbob Energy Corp | Artesia, NM 882110227 | Oil & Gas Operator | Oct 2010 |
| 450 | Marchman, J. E. | Graham, TX 76450 | Oil & Gas Operator | Jul 2009 |
| 451 | Marco Drilling Inc | Monroeville, PA 15146-0278 | Oil & Gas Operator | Dec 2024 |
| 452 | Marco Land & Petroleum, Inc. | | Oil & Gas Operator | Jun 2000 |
| 453 | Marco Oil Compan | | Oil & Gas Operator | Aug 1992 |
| 454 | Marco Oil Company | Sparta, KY 41086 | Oil Operator | Dec 2021 |
| 455 | Marco Oil Company LLC | Bartlesville, OK 74005 | Oil & Gas Operator | Nov 2025 |
| 456 | Marco Polo Exploration, Inc. | Rosenberg, TX 77471 | Oil & Gas Operator | Dec 1993 |
| 457 | Marco Production | | Oil & Gas Operator | Apr 1986 |
| 458 | Marcon Operating Company, Inc. | Bridgeport, TX 76426 | Oil & Gas Operator | Oct 2011 |
| 459 | Marconi Exploration, Inc. | Houston, TX 77056 | Oil & Gas Operator | Aug 1997 |
| 460 | Marcum Drilling Co. | Midland, TX 79701 | Oil & Gas Operator | Aug 2002 |
| 461 | Marcus Exploration Inc | Piedmont, OK 73078-0308 | Oil & Gas Operator | Dec 2000 |
| 462 | Mardale Drilling Company | Oklahoma City, OK 73157 | Oil Operator | Nov 1998 |
| 463 | Marden Petroleum Exp Co | Marietta, OH 45750 | Oil & Gas Operator | Dec 1990 |
| 464 | Marden Producing | | Gas Operator | Aug 1990 |
| 465 | Marden Producing Company | Edmond, OK 73083 | Gas Operator | Sep 2025 |
| 466 | Mare Energy | Danville, OH 43014 | Oil & Gas Operator | Dec 2021 |
| 467 | Mare Energy LLC | Danville, OH 43014 | Oil & Gas Operator | Dec 2024 |
| 468 | Marexco | | Oil & Gas Operator | Nov 1994 |
| 469 | Marexco, Inc. | Castle Rock, CO 80104 | Oil & Gas Operator | Sep 2025 |
| 470 | Margaret Merganser Inc | Tionesta, PA 16353-5853 | Oil & Gas Operator | Dec 2008 |
| 471 | Maria L. Andrade | | Oil Operator | Dec 2006 |
| 472 | Mariacher, Matthew | Elma, NY 14059 | Gas Operator | Dec 2023 |
| 473 | Mariah Energy Corp. | Austin, TX 78716 | Oil & Gas Operator | Apr 1999 |
| 474 | Mariah Exploration LLC | Pawhuska, OK 74056 | Oil & Gas Operator | Oct 2008 |
| 475 | Mariah Operating Company, LLC | Denver, CO 80201 | Oil & Gas Operator | Dec 2009 |
| 476 | Marianas Operating Co. | Abilene, TX 79601 | Oil & Gas Operator | Aug 2003 |
| 477 | Marieff Petroleum, Inc. | Sagamore Hills, OH 44067 | Gas Operator | Dec 2024 |
| 478 | Marienfeld Exploration | Houston, TX 77005 | Oil & Gas Operator | Mar 1994 |
| 479 | Marienfeld Exploration, Inc. | Ojai, CA 93024 | Oil & Gas Operator | Feb 2026 |
| 480 | Marietta Royalty Co Inc | Stillwater, OK 74076 | Oil & Gas Operator | Dec 1986 |
| 481 | Marina Pacifica Oil Company | | Oil & Gas Operator | Dec 1981 |
| 482 | Marine Cont. & Supply Inc. | | Oil & Gas Operator | Nov 1985 |
| 483 | Marine Properties, Inc. | | Oil & Gas Operator | Feb 1995 |
| 484 | Mariner Energy, Inc. | Houston, TX 77042 | Oil & Gas Operator | Nov 2010 |
| 485 | Marino, Charles B. | Tomball, TX 77377 | Oil & Gas Operator | Feb 2026 |
| 486 | Marion Corporation | | Oil & Gas Operator | Jan 2001 |
| 487 | Marion County Prod. Co., L.L.C. | Kilgore, TX 75663 | Oil & Gas Operator | Feb 2026 |
| 488 | Marion Energy Inc | Houston, TX 770082292 | Oil & Gas Operator | May 2015 |
| 489 | Marion Operating Corp | Marion, OH 43301 | Oil & Gas Operator | Dec 2020 |
| 490 | Mariposa Petroleum Co. | | Gas Operator | Dec 1980 |
| 491 | Maritech Resources, Inc. | The Woodlands, TX 77380 | Oil & Gas Operator | Nov 2009 |
| 492 | Maritech Resources, LLC | | Oil & Gas Operator | May 2011 |
| 493 | Marjac Energy Co | Bremen, OH 43107 | Oil & Gas Operator | Dec 1986 |
| 494 | Marjac Oil Company, Inc. | Breckenridge, TX 76424 | Oil & Gas Operator | Feb 2026 |
| 495 | Marjo Incorporat | | Oil & Gas Operator | Jun 1990 |
| 496 | Marjo Oil Company | Lockhart, TX 78644 | Oil & Gas Operator | Oct 1999 |
| 497 | Marjo Operating Company Inc | Tulsa, OK 741010729 | Oil & Gas Operator | Nov 2025 |
| 498 | Marjo Operating Mid-Continent LLC | Tulsa, OK 74103 | Oil & Gas Operator | Dec 2025 |
| 499 | Marjo, Inc. | | Oil & Gas Operator | Sep 1991 |
| 500 | Mark & Troy Johnson | Sugar Grove, PA 16350-5938 | Oil Operator | Dec 2025 |