| Conflict: | Battle of Arroyo Grande |
| Partof: | the Portuguese conquest of the Banda Oriental |
| Date: | 28 October 1818 |
| Place: | Arroyo Grande, Uruguay |
| Result: | Luso-Brazilian victory |
| Combatant1: | United Kingdom of Portugal, Brazil and the Algarves |
| Combatant2: | Federal League |
| Commander1: | Bento Manuel Ribeiro |
| Commander2: | Fructuoso Rivera |
| Strength1: | 4000 |
| Strength2: | Unknown |
| Casualties1: | Unknown |
| Casualties2: | ~100 |
The Battle of Arroyo Grande took place between the Luso-Brazilian forces under the command of Bento Manuel Ribeiro, and the Artiguist forces of Fructuoso Rivera in Arroyo Grande, modern-day Uruguay. The Luso-Brazilian forces were completely victorious.
After the Luso-Brazilian success in Arroyo Grande, a great number of Artiguist soldiers and officers defected and joined them, due to the fact they were promised forgiveness and mercy. This, together with the battle itself, was a severe blow to Artigas' war effort.