Abu Yusuf Yakub al-Mansur (reigned 1184-1199) was the third caliph of the Almohad dynasty and the victor against the Spanish Christians at the battle of Alarcos.

Abu Yusuf served as vizier of the Almohad empire during the reign of his father, Abu Yakub Yusuf (1162-1184), and at his death was chosen as his successor as Yakub I. Having gained considerable practical experience as an administrator in the vizierate, Yakub kept firm control of the state in his own hands, continuing the Almohad tradition of active leadership in religious affairs and vigorous military campaigns against the enemies of the state.

The first part of Yakub's reign was spent in repelling an offensive against Almohad territory in North Africa launched by the Banu Ghaniya, the Sanhaja Berbers who had continued Berber rule on the Balearic Islands. The attack came in 1185 against the eastern holdings of the Almohads on the Algerian...