Agoncillo is a town and municipality in the province of La Rioja, in northern Spain. It lies within the autonomous community of La Rioja, a small region in the Ebro River valley known for its wine production.
Like other municipalities in the province, Agoncillo is administered as a local entity with its own town council. La Rioja as a whole is one of Spain's smallest autonomous communities, and its settlements are typically small towns and villages set among farmland and river terrain.