Tres Ríos is a district of the La Unión canton, in the Cartago province of Costa Rica. Its name is derived from its location at the confluence of the Tiribí, Chiquito and Cruz rivers. According to the 2011 census, Tres Ríos had a population of 9,331 inhabitants. The district has an area of 2.19 km2 and an elevation of 1,345 metres.