Santa Eulalia de Oscos is a municipality in the Autonomous Community of the Principality of Asturias, in northern Spain. It lies in the western part of Asturias, within the comarca known as Oscos, a rural and mountainous area near the border with Galicia.
The municipality is bordered on the north by Villanueva de Oscos, on the east by Villanueva de Oscos, San Martín de Oscos and Grandas de Salime, and on the south and west by Lugo province in Galicia. Its position along the Galician border places it at the western edge of Asturias.
Like other municipalities in the Oscos area, Santa Eulalia de Oscos is a small, sparsely populated rural council made up of scattered parishes and hamlets rather than a single dense urban centre. Its setting is defined by the hilly terrain and green landscapes typical of this part of western Asturias.