| Tainhas River | |
| River System: | Das Antas River. |
| Mouth Coordinates: | -28.8119°N -50.6043°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Brazil |
Rio Tainhas (Portuguese: Rio Tainhas) is a river in the state of Rio Grande do Sul, Brazil. It is a left tributary of the Das Antas River
Part of the course of the river, including the Cachoeira do Passo do S, a waterfall, is protected by the Tainhas State Park, created in 1975.