San Tirso de Abres is a municipality in the Autonomous Community of the Principality of Asturias, Spain. It is the westernmost council in Asturias.
The municipality is bordered on the north, south, and west by the province of Lugo in Galicia, and on the east by the Asturian municipalities of Taramundi and Vegadeo. Its position places it at the far western edge of Asturias, adjacent to the Galician border on three sides.