Guillén Pérez de Guzmán (ca. 1180–1233), a member of the House of Guzmán, one of the most aristocratic of the Kingdom of Castile, was the maternal grandfather of Queen Beatrice of Castile, Queen Consort of Portugal as the wife of King Alfonso III. His father was Pedro Rodríguez de Guzmán—killed in the Battle of Alarcos on July 18, 1195 and son of Rodrigo Muñoz de Guzmán—and Mahalda With his brothers Nuño and Theobald, he fought alongside King Alfonso VIII at the decisive Battle of Navas de Tolosa in 1212. Even though his kinsmen supported the Laras during the crisis that ensued after the death of King Alfonso VIII, Guillén, probably because of his marriage to a member of the Girón clan, supported Queen Berengaria of Castile and her son, the future king Ferdinand III.
