| Associated Milk Producers Inc | Owner/operator | | | |
| Associated Milk Producers Inc Pipeline | Owner/operator | | | |
| Associated Natural Gas Co | Owner/operator | | | |
| Associated Pipe Line Contractors, Inc. | Contractor | Houston, TX | 28 | |
| Associated Pipeline | Contractor | | 1 | |
| Atchison Casting Corporation | Owner/operator | | | |
| Atchley Resources Inc. | Owner/operator | | | |
| Ati Metals | Owner/operator | Albany, OR | | 1 |
| Atinum Energy, Inc | Owner/operator | | | 2 |
| Atlanta Gas Light | Owner/operator | Atlanta, GA | 3 | 1 |
| Atlantic Coast Pipeline, LLC | Owner/operator | | 1 | |
| Atlantic Richfield Co | Owner/operator | | | |
| Atlas Asphalt Products Inc | Owner/operator | | | 1 |
| Atlas Barnett, LLC | Owner/operator | Pittsburgh, PA | | 1 |
| Atlas KS Energy LLC | Owner/operator | | | 1 |
| Atlas Oil & Gas Exploration, LLC | Owner/operator | | | 1 |
| Atlas Operating LLC | Owner/operator | Houston, TX | | 4 |
| Atlas Pipeline Mid-Continent WestTex, LLC | Owner/operator | | 1 | |
| Atlas Pipeline Mid-Continent Westok, LLC | Owner/operator | | | |
| Atlas Pipeline Mid-Continent, L.l.c. | Owner/operator | | | |
| Atlas Pipeline Tennessee, LLC | Owner/operator | Clinton, TN | | 1 |
| Atlas Roofing Corp | Owner/operator | | | 1 |
| Atlas Trenchless, LLC | Contractor | Cold Spring, MN | 4 | |
| Atmos Energy - Kentucky Division | Owner/operator | | | |
| Atmos Energy - Texas | Owner/operator | | | |
| Atmos Energy - West Texas | Owner/operator | Dallas, TX | | 1 |
| Atmos Energy - West Texas Division | Owner/operator | | | 8 |
| Atmos Energy --Louisiana Divison | Owner/operator | | | |
| Atmos Energy Corp ( Mid-Tex Division) Transmission (formerly Txu Gas Company) | Owner/operator | | | |
| Atmos Energy Corp - Louisiana Division | Owner/operator | | | |
| Atmos Energy Corp., Mid-Tex Div. | Owner/operator | | | 57 |
| Atmos Energy Corporation - Atmos Gathering Company, LLC | Owner/operator | Dallas, TX | | 1 |
| Atmos Energy Corporation - Atmos Pipeline And Storage, LLC | Owner/operator | Dallas, TX | | 1 |
| Atmos Energy Corporation - Colorado/kansas | Owner/operator | Dallas, TX | | 1 |
| Atmos Energy Corporation - Ky/mid-States (mid-States) | Owner/operator | Dallas, TX | | 2 |
| Atmos Energy Corporation - Ky/mid-States (wkg Storage) | Owner/operator | | | |
| Atmos Energy Corporation - Ky/mid-States Division | Owner/operator | | | |
| Atmos Energy Corporation - Louisiana | Owner/operator | Dallas, TX | | 1 |
| Atmos Energy Corporation - Mid-Tex | Owner/operator | Dallas, TX | | 1 |
| Atmos Energy Corporation - Mississip | Owner/operator | | | 2 |
| Atmos Energy Corporation - Mississippi | Owner/operator | Dallas, TX | | 1 |
| Atmos Energy Corporation - Mississippi Division | Owner/operator | | | |
| Atmos Energy Corporation - Trans Louisiana Gas Pipeline | Owner/operator | | | |
| Atmos Energy Corporation -Colorado - Kansas Division | Owner/operator | | | |
| Atmos Energy Corporation Midstates Division | Owner/operator | | | |
| Atmos Energy Corporation, Mid-Tex Division | Owner/operator | | | |
| Atmos Energy Inc | Owner/operator | | 5 | 9 |
| Atmos Pipeline - Texas | Owner/operator | Dallas, TX | 1 | 1,171 |
| Atmos Pipeline and Storage, LLC | Owner/operator | | 2 | |
| Atoka Midstream LLC | Owner/operator | | | 1 |