al- Mansur (äl-mänsŏŏr´) [Arab.,=the victorious], d. 775, 2d Abbasid caliph (754–75) and founder of the city of Baghdad. His name was in full Abu Jafar abd-Allah al-Mansur. He was brother and successor of Abu al-Abbas. A vigorous and dominating caliph, he successfully consolidated his empire even though it was threatened by internal strife and foreign wars. He could not prevent the secession of Muslim Spain, however, under the Umayyad prince Abd ar-Rahman I. Mansur lived at first, as his brother had, near Kufa, but in 762 he began to build a new city, Baghdad.

al- Mansur (Muhammad ibn Abi-Amir al-Mansur billah), 914–1002, Moorish regent of Córdoba, known in Spanish as Almanzor. He became steward to Princess Subh, wife of the caliph Hakim II, and under her patronage and by clever manipulation he rose to become (978) royal chamberlain for Hakim's successor, the young Hisham II. Al-Mansur kept Hisham in seclusion at his court and assumed complete control over the caliphate. A great warrior, he reorganized the army and undertook many campaigns against the Christian states of N Spain; he sacked Barcelona (985), razed the city of León (988), and destroyed the church and shrine of St. James at Santiago de Compostela (998). Before he died he appointed one of his sons as his successor.