| Ogarantim River | |
| Other Name: | Fortaleza River |
| Source1 Location: | Rio Grande do Sul state |
| Mouth: | Guarita River |
| Subdivision Type1: | Country |
| Subdivision Name1: | Brazil |
The Ogarantim or Ogaratim River, also known as the Fortaleza River, is a river of Rio Grande do Sul state in southern Brazil.