Sebastián Garcilaso de la Vega y Vargas (1507 in Badajoz, Extremadura, Spain – 1559 in Cuzco, Viceroyalty of Peru) was a Spanish conquistador and colonial official.
He fathered a son, the mestizo chronicler Garcilaso de la Vega, with the Inca princess Isabel Chimpu Occlo.
He served with Pedro de Alvarado, and participated in the conquests of Hernán Cortés, first in Mexico and later in Guatemala.
After receiving orders to conquer the Cauca River valley, he abandoned the attempt to colonize the San Mateo Bay, returning to Lima with his eighty men to encounter Manco Inca Yupanqui.
He participated in the expedition to the Collao, along with Gonzalo Pizarro and Pedro de Oñate, defeating Tiso Yupanqui in the battle of Cochabamba.