Ain (; Arpitan: En) is a department named after the Ain River on the eastern edge of France. Being part of the region Auvergne-Rhône-Alpes and bordered by the rivers Saône and Rhône, the department of Ain enjoys a privileged geographic situation. It has an excellent transport network (TGV, highways) and benefits from the proximity to the international airports of Lyon and Geneva.

Aín (Spanish: Ahín) is a town in eastern Spain, in the province of Castellón, part of the autonomous community of Valencia.

Ain is a département of France.