San Antonio Oeste is a port city in the Argentine province of Río Negro, and head of the department of San Antonio. The town is bordered by its sister communities of San Antonio Este, to the east, and Las Grutas, to the southwest. Discovered by an expedition of the Spanish Empire in 1779, San Matías Gulf became the site of an outpost, San Antonio. Water scarcity led the original settlement to fail in 1905, leading the community to settle west of the gulf, in what today is San Antonio Oeste.