Calvillo (Spanish ) is a municipality in the Mexican state of Aguascalientes. The city of Calvillo, the second largest in the state, serves as the municipal seat. It is located to the western part of the state, at about 52 kilometers of the city of Aguascalientes. It stands at 21°51′N 102°43′W / 21.850°N 102.717°W in the southwestern corner of the state. It is bounded by Jalisco and Zacatecas. The municipality, which has an area of 931.26 km² (359.56 sq mi), reported a population of 54,136 by 2010. The town of Ojocaliente is another significant community in the municipality. Calvillo is one of the richest, most prosperous municipalities in Aguascalientes.