The Co-cathedral of Santa María de la Fuente la Mayor (Spanish: Concatedral de Santa María de la Fuente la Mayor) is a co-cathedral located in Guadalajara, in Castile-La Mancha, Spain. It is in the Roman Catholic Diocese of Sigüenza-Guadalajara.

The building is in mudejar style. It was declared Bien de Interés Cultural in 1941.