Isla Mayor is a municipality located in the province of Seville, Spain.

The main village is Isla Mayor, about 45 km south west of Sevilla, The small village of Poblado de Alfonso XIII is in the same municipality.

Isla Mayor separated from the municipality of Puebla del Rio in 1994.

It is crisscrossed by canals, and the land dedicated primarily to the cultivation of rice.

The village and municipality were known as Villafranco del Guadalquivir, in honour of the dictator General Franco.