| Lake | County | Latitude | Longitude |
| O Brien Lake | Burleigh | 47.259099 | -100.367550 |
| O Connell Lake | Benson | 48.183495 | -99.266834 |
| Oahe Reservoir | Emmons | 45.959197 | -100.482660 |
| Oak Lakes | Rolette | 48.960588 | -99.801777 |
| Olson Slough | Stutsman | 46.822093 | -99.107807 |
| Omlid Slough | Nelson | 47.740743 | -98.008753 |
| Oslie Lake | McHenry | 48.229347 | -100.861085 |
| Ottofy Lake | Nelson | 47.742586 | -98.380008 |