| 801 | Lyco Operating Company | Dallas, TX 75206 | Gas Operator | Dec 1997 |
| 802 | M & C Oil Inc | Indianola, NE 68034 | Oil & Gas Operator | Nov 2013 |
| 803 | M & G Oil And Gas Inc | Llabarge, WY 83123 | Oil & Gas Operator | Apr 2023 |
| 804 | M & K Oil Company LLC | Gillette, WY 82716 | Oil & Gas Operator | Apr 2026 |
| 805 | M & K Oil Operations | | Oil & Gas Operator | Sep 1994 |
| 806 | M G Production Co | Rock Springs, WY 82901 | Oil Operator | Dec 1999 |
| 807 | M K M Oil Company | Casper, WY 82602 | Oil & Gas Operator | Jun 1996 |
| 808 | M W Petroleum Company | Houston, TX 77056 | Oil & Gas Operator | Dec 1995 |
| 809 | M-3 Industries | Casper, WY 82602 | Oil & Gas Operator | Jan 2026 |
| 810 | M2S Oil LLC | | Oil Operator | Apr 2026 |
| 811 | Mack Energy Corporation | Artesia, NM 88211 | Oil & Gas Operator | Apr 2026 |
| 812 | Macum Energy Inc | Billings, MT 59104 | Oil & Gas Operator | Aug 2021 |
| 813 | Maguire Oil Company | Dallas, TX 75270 | Oil & Gas Operator | Mar 2015 |
| 814 | Maha Energy Us Inc | | Oil Operator | Nov 2023 |
| 815 | Main Energy, Inc. | Houston, TX 77079 | Oil & Gas Operator | May 2009 |
| 816 | Majestic Petroleum Operations Inc | Story, WY 82842 | Gas Operator | Mar 2007 |
| 817 | Mak-J Energy Wyoming LLC | Denver, CO 80620 | Oil & Gas Operator | Nov 2012 |
| 818 | Mallon Oil Company | Denver, CO 80202 | Oil & Gas Operator | Jun 2005 |
| 819 | Manewal Bradley Oil Company | Newcastle, WY 82701 | Oil & Gas Operator | Aug 2013 |
| 820 | Manx Oil Corporation | Casper, WY 82601 | Oil & Gas Operator | Jun 2010 |
| 821 | Mapco Oil Company | | Oil & Gas Operator | Jan 1985 |
| 822 | Mar/Reg Investments | Irving, TX 75016 | Oil & Gas Operator | Jul 1999 |
| 823 | Marathon Oil Company | Houston, TX 77252 | Oil & Gas Operator | Apr 2026 |
| 824 | Markus Production | Littleton, CO 80123 | Oil & Gas Operator | Jan 2026 |
| 825 | Marlin Oil Company LLC | Gillette, WY 82718 | Oil & Gas Operator | Mar 2023 |
| 826 | Marmik Oil Company | El Dorado, AR 71730 | Oil & Gas Operator | Jan 2015 |
| 827 | Marquis-Allred Eng Inc | | Oil & Gas Operator | Apr 1992 |
| 828 | Marshall & Winston, Inc. | Midland, TX 79710 | Oil & Gas Operator | Apr 2026 |
| 829 | Martens & Peck Operating Co | | Gas Operator | Feb 1997 |
| 830 | Martens & Peck Production Co | Denver, CO 80222 | Oil & Gas Operator | Feb 1997 |
| 831 | Martin Exploration | Westminster, CO 80030 | Oil & Gas Operator | Dec 1993 |
| 832 | Materi Exploration Inc | Upton, WY 82730 | Oil Operator | Nov 2021 |
| 833 | Matrix Production Company | Sugar Land, TX 77478 | Oil & Gas Operator | Apr 2026 |
| 834 | Maxim Drilling & Expl Inc | Gillette, WY 82717 | Oil & Gas Operator | Mar 2026 |
| 835 | Maximus Operating, LTD. | Kilgore, TX 75663 | Oil & Gas Operator | Jun 2026 |
| 836 | Mbi Oil & Gas LLC | Dickinson, ND 58601 | Oil & Gas Operator | Apr 2026 |
| 837 | McAdams Roux & Associates | Denver, CO 80202 | Oil & Gas Operator | Dec 1999 |
| 838 | McCartney Engineering LLC | Wheat Ridge, CO 80033 | Oil & Gas Operator | Feb 2026 |
| 839 | McClure Enterprises | Recluse, WY 82725 | Oil & Gas Operator | Dec 2025 |
| 840 | McCulliss Resource Company Inc | Denver, CO 80202 | Oil & Gas Operator | Jun 1999 |
| 841 | McEna Inc | Tulsa, OK 74135 | Oil & Gas Operator | Jul 2005 |
| 842 | McGuire John C | Gillette, WY 82717 | Oil & Gas Operator | Oct 2005 |
| 843 | McKenzie Production Company | Houston, TX 77063 | Oil & Gas Operator | May 1995 |
| 844 | MCL 1 Oil & Gas Wyoming LLC | Minneapolis, MN 55402 | Oil & Gas Operator | Jul 2018 |
| 845 | MCM Operating LLC | Midland, TX 79702 | Oil & Gas Operator | Mar 2026 |
| 846 | McMahon-Bullington LP | Wichita Falls, TX 76307 | Oil & Gas Operator | Apr 2009 |
| 847 | McMurry Energy Company | | Oil & Gas Operator | Dec 2001 |
| 848 | McMurry Oil LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2004 |
| 849 | McO Resources Corporation | | Oil & Gas Operator | Feb 1986 |
| 850 | McQueen Ed & Company Inc | Lindsey, OK 73052 | Oil & Gas Operator | Apr 2014 |
| 851 | McRae & Henry LTD | Golden, CO 80401 | Oil & Gas Operator | May 2022 |
| 852 | MDS Energy Development LLC | | Oil & Gas Operator | Mar 2026 |
| 853 | Meadow Deep LLC | | Oil & Gas Operator | Apr 2026 |
| 854 | Medallion Exploration | Holladay, UT 84117 | Oil & Gas Operator | Dec 2015 |
| 855 | Medallion Petroleum, Inc. | Tulsa, OK 74103 | Oil & Gas Operator | Jan 2015 |
| 856 | Medallion Production Company | Tulsa, OK 74103 | Oil & Gas Operator | May 1997 |
| 857 | Medicine Bow Operating Company | Houston, TX 77002 | Oil & Gas Operator | Apr 2014 |
| 858 | Meerkat Logistics And Operations LLC | Tuscaloosa, AL 35401 | Oil Operator | Jan 2026 |
| 859 | Mega Energy LLC | Gillette, WY 82718 | Gas Operator | Apr 2026 |
| 860 | Mels Water Service Inc | Lysite, WY 82642 | Oil Operator | Mar 2013 |
| 861 | Memorial Exploration Company | Saint Louis, MO 63105 | Oil & Gas Operator | Aug 1996 |
| 862 | Memorial Production Operating LLC | Houston, TX 77002 | Oil & Gas Operator | Jun 2026 |
| 863 | Merit Energy Company | Dallas, TX 75240 | Oil & Gas Operator | Jun 2026 |
| 864 | Merit Productions | | Oil Operator | Sep 1996 |
| 865 | Meritage Energy Company LLC | Denver, CO 80202 | Oil & Gas Operator | May 2013 |
| 866 | Meritage Energy Partners LLC | Denver, CO 80202 | Oil & Gas Operator | Dec 2005 |
| 867 | Merrico Resources | | Oil Operator | Mar 1992 |
| 868 | Merrion Oil & Gas Corp | Farmington, NM 87401 | Oil & Gas Operator | Mar 2026 |
| 869 | Methane Productions Inc | Recluse, WY 82725 | Oil & Gas Operator | Apr 2007 |
| 870 | Meyer Douglas P | Longmont, CO 80501 | Oil & Gas Operator | Aug 2006 |
| 871 | Mi3 Energy LLC | | Oil & Gas Operator | Apr 2026 |
| 872 | Michigan-Wisconsin Pipe Line Co | | Oil & Gas Operator | Dec 1983 |
| 873 | Mid Central Production LLC | Evanston, WY 82930 | Oil Operator | Dec 2025 |
| 874 | Mid-Con Energy Operating, LLC | Tulsa, OK 74136 | Oil & Gas Operator | Apr 2026 |
| 875 | Midgard Energy Company | The Woodlands, TX 77380 | Oil & Gas Operator | Dec 2014 |
| 876 | Millennium Oil & Gas LLC | Denver, CO 80203 | Oil & Gas Operator | Oct 2025 |
| 877 | Mineral Resources & Engineering | Aladdin, WY 82710 | Oil Operator | Jul 1991 |
| 878 | Mingo Oil Producers | Salt Lake City, UT 84111 | Oil & Gas Operator | Nov 1987 |
| 879 | Minnelusa Oil LLC | Temecula, CA 92589 | Oil Operator | Feb 2002 |
| 880 | Misahar Investments | Evergreen, CO 80439 | Oil Operator | Dec 1992 |
| 881 | Mitchell Energy Corp | Houston, TX 77002 | Oil & Gas Operator | Aug 2013 |
| 882 | Mitchell M J | | Oil & Gas Operator | Jan 1983 |
| 883 | MKM Services Inc | | Oil Operator | Apr 2026 |
| 884 | Mobil Expl & Producing North America Inc | | Oil & Gas Operator | Nov 1986 |
| 885 | Moco Oil Inc | | Oil Operator | May 1984 |
| 886 | Mon-Oil Inc | | Oil & Gas Operator | Apr 1996 |
| 887 | Monahan Rex | Sterling, CO 80751 | Oil & Gas Operator | Jun 2002 |
| 888 | Moncrief W A Jr | Fort Worth, TX 76102 | Oil & Gas Operator | Apr 2026 |
| 889 | Monsanto Company | Indianapolis, IN 46280 | Oil & Gas Operator | Jan 2005 |
| 890 | Montana Power Company | Butte, MT 59701 | Oil & Gas Operator | Apr 2002 |
| 891 | Montex Drilling Company LLC | Fort Worth, TX 76102 | Oil & Gas Operator | Jun 2026 |
| 892 | Montex Exploration | Sugarland, TX 77478 | Oil Operator | Apr 2003 |
| 893 | Monument Global Resources Inc | Dallas, TX 75243 | Oil & Gas Operator | Jan 2025 |
| 894 | Morgan Energy Corporation | Englewood, CO 80110 | Oil & Gas Operator | Mar 2006 |
| 895 | Morning Star Oil Company | Thermopolis, WY 82443 | Oil Operator | Feb 2025 |
| 896 | Morsey Oil & Gas Corporation | Corpus Christ, TX 78401 | Oil & Gas Operator | Jun 2026 |
| 897 | Mosbacher Production Co. | Houston, TX 77001 | Oil & Gas Operator | Aug 1984 |
| 898 | Moss Properties Inc | | Oil & Gas Operator | Mar 1986 |
| 899 | Mountain Hawk Energy LLC | Athens, TX 75751 | Gas Operator | Jan 2015 |
| 900 | Mountain Petroleum Corp | Denver, CO 80202 | Oil & Gas Operator | Apr 2013 |