The Battle of Ksar El Kebir, also known as Battle of Three Kings, or "Battle of Oued El Makhazeen" in Morocco, and Battle of Alcácer Quibir in Portugal (variant spellings are legion: Alcácer-Quivir, Alcazarquivir, Alcassar, meaning grand castle in Arabic), is fought in northern Morocco, near the town of Ksar-el-Kebir and Larache, on 4 August 1578.

The combatants are the army of the deposed Moroccan Sultan Abu Abdallah Mohammed II, with his ally, the King of Portugal Sebastian I, and a large Moroccan army nominally under the new Sultan of Morocco (and uncle of Abu Abdallah Mohammed II) Abd Al-Malik I.The Christian king, Sebastian I, had planned a crusade after Abu Abdallah asked him to help recover his throne.

Abu Abdallah's uncle, Abd Al-Malik, had taken it from him with Ottoman support.

The defeat of Portugal leads to the end of the Aviz dynasty, and the integration of the country in the Iberian Union for 60 years under the Philippine Dynasty in a dynastic union with Spain.