Bailo is a municipality in the province of Huesca, in the autonomous community of Aragon, Spain. It is located in the northeastern part of the country, within the comarca of Jacetania, in the foothills of the Pyrenees near the Aragón river valley.
According to the 2024 census (INE), the municipality has a population of 263 inhabitants. Like many small municipalities in the Aragonese Pyrenees, Bailo is made up of a compact historic core along with scattered hamlets and farmsteads across its surrounding rural territory.
The village lies on the Camino de Santiago, the pilgrimage route to Santiago de Compostela, which passes through this part of Aragon. Its economy has traditionally been based on agriculture and livestock, though tourism related to the pilgrimage route and the surrounding mountain landscape now also plays a role.