| Matalco Inc. MLX Pipeline Project | Dominion East Ohio | OH | | |
| Matterhorn Express Pipeline | WhiteWater | TX | 2023–2024 | |
| Matterhorn Express Pipeline | WhiteWater Midstream | TX | In service 2024 | |
| Maumee River Crossing Project | Columbia Gas of Ohio | OH | | |
| Maurepas Pipeline coastal use permit P20170318 pipeline | Maurepas Pipeline, LLC | LA | | |
| Maurepas Pipelines Project | Maurepas Pipeline, LLC | LA | | |
| Maverick Basin Trunkline | | TX | | |
| Maxbass Station Construction - Bottineau County | North Dakota Pipeline Company LLC | ND | | |
| Mayfield LP Pipeline | Antero Midstream LLC | WV | | |
| Maysville Project | Columbia Gulf Transmission, LLC | KY | | |
| McAlester Fuel coastal use permit P20011424 pipeline | McAlester Fuel Company | LA | | |
| McAlester Fuel coastal use permit P20021260 pipeline | McAlester Fuel Company | LA | | |
| McAlester Fuel coastal use permit P20021410 pipeline | McAlester Fuel Company | LA | | |
| McCleary No. 5 Conversion Project | Northern Natural Gas Company | IA | Started 2021 | |
| McCleary Well Conversion Project | Northern Natural Gas Company | IA | Started 2016 | |
| McCloud Lateral Project | El Paso Natural Gas Company, L.L.C. | | | |
| McComb Compressor Station Reliability Project | Gulf South Pipeline Company, LLC | MS | In service 2021 | |
| McKinleyville to Mingo NU Pipeline | Appalachia Midstream Services, L.l.c. | WV | | |
| McMoran Oil & Gas coastal use permit P19960659 pipeline | McMoran Oil & Gas Co | LA | | |
| McMoran Oil & Gas coastal use permit P20060443 pipeline | McMoran Oil & Gas Co | LA | | |
| McMoran Oil & Gas coastal use permit P20070489 pipeline | McMoran Oil & Gas Co | LA | | |
| McRae Exploration & Production coastal use permit P20170357 pipeline | McRae Exploration & Production, Inc. | LA | | |
| Means Compressor Station | | KY | In service 2017 | |
| Meathouse Fork Compressor Station | Stonewall Gas Gathering LLC | WV | | |
| Medicine Bow Expansion Project | Wyoming Interstate Company, L.L.C. | WY | In service 2008 | |
| Medicine Bow Lateral | Wyoming Interstate Company, L.L.C. | CO, WY | In service 1999 | |
| Medicine Bow Lateral Expansion | Wyoming Interstate Company, L.L.C. | CO, WY | In service 2001 | |
| Medina New Drills Project | Columbia Gas Transmission, LLC | | | |
| Meeker Lateral | Enterprise | CO | | |
| Meeker Station to Meeker Hub Pipeline | Encana | CO | | |