| Lake | County | Latitude | Longitude |
| Abandoned Lake | Carbon | 45.009633 | -109.603058 |
| Abbot Lake | Flathead | 48.117605 | -114.052389 |
| Abey Reservoir | Valley | 48.557556 | -106.892064 |
| Absolen Reservoir | Rosebud | 46.537321 | -106.759492 |
| Ackley Lake | Judith Basin | 46.953387 | -109.938967 |
| Ahorn Bastn | Lewis and Clark | 47.493436 | -113.046381 |
| Ajax Lake | Beaverhead | 45.329226 | -113.727434 |
| Akokala Lake | Flathead | 48.878752 | -114.198702 |
| Albicaulis Lake | Granite | 46.332382 | -113.061304 |
| Albino Lake | Carbon | 45.014097 | -109.580337 |
| Albro Lake | Madison | 45.594227 | -111.967999 |
| Aldridge Lake | Park | 45.091386 | -110.811623 |
| Allison Lake | Glacier | 48.672517 | -112.398943 |
| Almeda Lake | Flathead | 48.255707 | -113.704869 |
| Aloe Lake | Toole | 48.623679 | -112.001629 |
| Alpha Lake | Flathead | 48.320680 | -114.044822 |
| Altoona Lake | Granite | 46.387324 | -113.111999 |
| Alvord Lake | Lincoln | 48.494446 | -115.883349 |
| Anderson Lake | Lewis and Clark | 47.471016 | -112.588911 |
| Anderson Reservoir | Blaine | 48.253499 | -108.950417 |
| Anita Reservoir | Yellowstone | 45.932371 | -108.004087 |
| Antone Reservoir | Garfield | 46.901602 | -106.567712 |
| Anvil Lake | Park | 45.100280 | -109.963512 |
| Aquarius Lake | Park | 45.057932 | -109.812088 |
| Arch Lake | Carbon | 45.159271 | -109.739460 |
| Arrambide Reservoir | Valley | 48.042148 | -107.015072 |
| Arrapooash Lake | Stillwater | 45.246208 | -109.847972 |
| Ashley Lake | Flathead | 48.201046 | -114.599453 |
| Ashley Lakes | Lake | 47.377179 | -113.963988 |
| Asteroid Lake | Stillwater | 45.271671 | -110.015726 |
| Aufwuchs Lake | Stillwater | 45.216365 | -110.047342 |
| Avalanche Lake | Madison | 44.892706 | -111.437166 |
| Avalanche Lakes | Carbon | 45.156307 | -109.791454 |
| Axolotl Lakes | Madison | 45.234218 | -111.873108 |
| Ayers Reservoir | Meagher | 46.653911 | -111.216020 |