Lope de Aguirre (c. 1510 – 27 October 1561) was a Spanish Basque conquistador in South America. Sent, along other rebellious settlers, to an impossible mission in search of the mythical Eldorado in the Amazon river, he eventually became their leader and rebelled against Philip II, being finally defeated and slain. Aguirre was born circa 1510 in Araotz Valley, in the Basque province of Guipúzcoa, part of the kingdom of Castile. (Today, Araotz belongs to the near municipality of Oñati, in northern Spain.) He was the son of a nobleman, with some culture, possibly from a family of court clerks. Aguirre was in his twenties and living in Seville when Hernándo Pizarro returned from Peru and brought back the treasures of the Incas, inspiring Aguirre to follow in his footsteps.
Aguirre probably enlisted himself in an expedition of 250 men chosen under Rodrigo Buran. He arrived in Peru in 1536 or 1537. In Cuzco, among other activities, Aguirre was responsible for the training of stallions. As a conquistador, however, he soon became infamous for his violence, cruelty and sedition. In 1544, Aguirre was at the side of Peru's first viceroy, Blasco Núñez Vela, who had arrived from Spain with orders to implement the New Laws, suppress the Encomiendas, and liberate the natives.