Plan is a municipality in the Sobrarbe comarca, in the province of Huesca, within the autonomous community of Aragon, Spain. It lies in the Pyrenees and serves as the main populated centre of the Gistau Valley (Valle de Gistau). Its postal code is 22367.
According to the 2010 census, the municipality had a population of 336 inhabitants. That figure reflects the small, dispersed settlement pattern typical of this mountainous part of northern Huesca, where the municipal territory includes several minor villages and hamlets grouped around the principal nucleus.
Plan's position in the Gistau Valley places it among the high Pyrenean valleys of Sobrarbe, a comarca known for its rugged terrain and traditional mountain settlements. As the valley's main population centre, it functions as the local administrative and service hub for the surrounding area.