San Xoán de Río is a municipality in Spain, located in the province of Ourense, in the autonomous community of Galicia. It covers an area of 61,14 km² and has a population of 811 inhabitants, resulting in a population density of 14,11 inhabitants per km². The municipality is situated approximately 70 km east of Ourense, nestled between two of the region's main waterways: the Navea River to the east and the Sil River to the west.
Among the most important localities within the municipality are the villages of Mouruás, San Silvestre de Argas, Seoane de Argas, Outeiro, O Campo, Cerdeira, O Aciveiro, Sabugueiro de Abaixo, and Sabugueiro de Arriba, among others.
San Xoán de Río is home to a rich archaeological and historical heritage. Among its most notable treasures is the legendary Sword of Mouruás, discovered in the village of Mouruás in the 1960s. This bronze sword belongs to the tradition of Central European bronze swords from the Iron Age. The municipality also boasts a wealth of Roman-era archaeological sites and Neolithic monuments, further highlighting its extensive historical significance.