Aarón Castellanos is a municipality in the General López Department of Santa Fe Province, in northeastern Argentina.

On 23 March 1903, the Argentinian aristocrat Mercedes Castellanos de Anchorena ordered her representative, Angel Leanes, to found a new town at the Soler stop of the Buenos Aires and Pacific Railway line.

It was to be named Aarón Castellanos, in honour of the founder of Esperanza, the colony which initiated Santa Fe's colonization.

A month later, on 29 April 1903, the bishop of Santa Fe approved Anchorena's plan for the foundation of a missionary convent.

At the time, the Franciscan community had an important presence in the area, not just fulfilling their religious and spiritual duties but also acting as administrators and controllers for the materials sent by Anchorena for the convent's construction.