| Aga | |
| Mouth: | Onon |
| Mouth Coordinates: | 51.5314°N 115.8356°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Russia |
| Length Km: | 167 |
| Basin Size Km2: | 8000 |
The Aga (ru|Ага; bua|Ага гол, Aga gol) is a river in Zabaykalsky Krai in Russia. It flows into the Onon. It is long, and has a drainage basin of .