| Official Name: | Ust-Zagan |
| Native Name: | Усть-Заган |
| Settlement Type: | Selo |
| Pushpin Map: | Russia Buryatia#Russia |
| Subdivision Type: | Country |
| Subdivision Name: | Russia |
| Subdivision Name1: | Republic of Buryatia |
| Subdivision Name3: | Bichursky District |
| Subdivision Type4: | Municipality |
| Utc Offset1: | +8:00 |
| Coordinates: | 50.6833°N 162°W[1] |
Ust-Zagan (Russian: Усть-Заган) is a rural locality (a selo) in Bichursky District, Republic of Buryatia, Russia. The population was 32 as of 2010.[2] There is 1 street.
Ust-Zagan is located 34 km northeast of Bichura (the district's administrative centre) by road. Uzky Lug is the nearest rural locality.[3]