| Abbreviation | Definition |
|---|---|
| GBRA | Guadalupe-Blanco River Authority |
| GBTA | Greater Bridgeport Transit Authority |
| GCA | Gulf Coast Authority |
| GCAA | Gambia Civil Aviation Authority |
| GCAA | General Civil Aviation Authority |
| GCAA | Ghana Civil Aviation Authority |
| GCAA | Guyana Civil Aviation Authority |
| GCDA | Greater Cochin Development Authority |
| GCHA | Garfield County Housing Authority |
| GCHA | Grand County Housing Authority |
| GCHA | Grundy County Housing Authority |
| GDA | General Disposal Authority |
| GECA | Georgia Emergency Communications Authority |
| GEMA | Gas and Electricity Markets Authority |
| GFZA | Ghana Free Zones Authority |
| GHA | Gibraltar Health Authority |
| GHA | Greenville Health Authority |
| GILCA | Grand Island Livestock Complex Authority |
| GLA | Gangmasters Licensing Authority |
| GLWA | Great Lakes Water Authority |