The Battle of Colhuacatonco was fought on 30 June 1521 during the late stages of the Siege of Tenochtitlan between Spanish-Tlaxcalan forces and the Mexica Empire (also typically referred as Aztec Empire). It is regarded as the most important victory achieved by the Mexica during the siege. Though much of the fighting occurred elsewhere in Tlatelolco, northern Tenochtitlan and Tacuba, the battle became known as such because most of the fighting occurred in this neighborhood; the Spaniards suffered their worst losses in this battle in this site.