| Monday River | |
| Mouth: | Parana River |
| Mouth Coordinates: | -25.6082°N -54.5985°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | Paraguay |
The Monday in Guarani pronounced as /mondaˈɨ / River is a river of Paraguay. It flows and empties into the Parana River, just south of the tri-border mark point of the Triple Frontier. Its primary course lies almost entirely within the Alto Parana Department.