| São Marcos River | |
| Source1 Location: | Goiás state |
| Mouth Location: | Paranaíba River |
| Subdivision Type1: | Country |
| Subdivision Name1: | Brazil |
The São Marcos River (Portuguese, Rio São Marcos) is a river of Goiás state in central Brazil. It is a tributary of the Paranaíba River, which it joins in the reservoir created by Emborcação Dam.