| Official Name: | Ust-Dunguy |
| Native Name: | Усть-Дунгуй |
| Settlement Type: | Selo |
| Pushpin Map: | Russia Buryatia#Russia |
| Subdivision Type: | Country |
| Subdivision Name: | Russia |
| Subdivision Name1: | Republic of Buryatia |
| Subdivision Name3: | Kyakhtinsky District |
| Subdivision Type4: | Municipality |
| Utc Offset1: | +8:00 |
| Coordinates: | 49.9833°N 147°W[1] |
Ust-Dunguy (Russian: Усть-Дунгуй; Buriat: Дунгуйн Адаг, Dunguin Adag) is a rural locality (a selo) in Kyakhtinsky District, Republic of Buryatia, Russia. The population was 712 as of 2010.[2] There are 5 streets.
Ust-Dunguy is located 124 km southeast of Kyakhta (the district's administrative centre) by road. Anagustay is the nearest rural locality.[3]