The Colegio Mayor de San Ildefonso (Spanish: Colegio Mayor de San Ildefonso) is a building located in Alcalá de Henares, Spain. It was declared Bien de Interés Cultural in 1914.^{[citation needed]}

Colegio Mayor de San Ildefonso
Native name Spanish: Colegio Mayor de San Ildefonso
Location	Alcalá de Henares, Spain
Coordinates	40°28′58″N 3°21′47″W / 40.482855°N 3.363075°W / 40.482855; -3.363075
Spanish Cultural Heritage
Official name	Colegio Mayor de San Ildefonso
Type	Non-movable
Criteria	Monument
Designated	1914
Reference no.	RI-51-0000132
Location of Colegio Mayor de San Ildefonso in Spain

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It was built by Cardinal Cisneros who commissioned architect Pedro de Gumiel to design. The foundation stone was laid in 1499, the Saint Ildefonsus` Chapel was completed in 1510; in 1516 began construction of the Paraninfo (Auditorium) and in 1537 Rodrigo Gil de Hontañón designed the main façade.

Although most of the work had been carried out by 1617 when Juan Gómez de Mora redesigned the courtyard (Thomas of Villanova's courtyard), the construction was not finished until the second half of the 17th century.