Spanish adventurer whose name practically became synonymous with cruelty and treachery in colonial Spanish America.

Nothing is known of Aguirre's life prior to 1544, when he arrived in Peru and took part in the Spanish suppression of Indian rebellions and in the wars that continually broke out between the Spanish conquerors. On Sept. 26, 1560, he joined an expedition led by Pedro de Ursúa to find the legendary kingdom of Eldorado, which was thought to be located at the headwaters of the Amazon River. Upon reaching the headwaters, Aguirre incited a rebellion in which Ursúa was killed. He then killed Fernando de Guzmán, who had succeeded Ursúa, and took command of the expedition.

Aguirre was considered to be a thoroughly disreputable character. It was said that Aguirre had all those members of the expedition who had opposed his plans, including several priests, put to death. He is then thought to have raided several towns in what is now Venezuela before he was finally caught and executed by the Spaniards. It is also believed that he killed his own daughter immediately prior to his capture. Aguirre's story is recounted with much poetic license in Werner Herzog's film Aguirre, the Wrath of God (1972).