The Spanish conqueror of Mexico was Hernán Cortes, also known as Hernando or Fernando CORTEZ. He was a Spanish conquistador who led an expedition that caused the fall of the Aztec Empire and brought large portions of mainland Mexico under the rule of the King of Castile in the early 16th century. Cortes was born in Medellín, Spain in 1485 and arrived in the New World in 1504. He is credited with the conquest of the Aztec Empire in 1521.