Abū Jaʿfar ʿAbd Allāh ibn Muḥammad al-Manṣūr usually known simply as by his laqab al-Manṣūr (المنصور) was the second Abbasid caliph, reigning from 136 AH to 158 AH succeeding his brother al-Saffah. He is known for founding the 'Round City' of Madinat al-Salam, which was to become the core of imperial Baghdad.

The Abbasid Caliphate or Abbasid Empire was the third caliphate to succeed the Islamic prophet Muhammad. It was founded by a dynasty descended from Muhammad's uncle, Abbas ibn Abd al-Muttalib, from whom the dynasty takes its name. They ruled as caliphs for most of the caliphate from their capital in Baghdad in modern-day Iraq, after having overthrown the Umayyad Caliphate in the Abbasid Revolution of 750 CE (132 AH). The Abbasid Revolution had its origins and first successes in the easterly region of Khorasan, far from the bases of Umayyad power in Syria and Iraq. The Abbasid Caliphate first centered its government in Kufa, modern-day Iraq, but in 762 the caliph Al-Mansur founded the city of Baghdad, near the ancient Babylonian capital city of Babylon and Persian city of Ctesiphon. Baghdad became the center of science, culture, and invention in what became known as the Golden Age of Islam. It was also during this period that Islamic manuscript production reached its height. Between the 8th and 10th centuries, Abbasid artisans pioneered and perfected manuscript techniques that became standards of the practice. This, in addition to housing several key academic institutions, including the House of Wisdom, as well as a multiethnic and multi-religious environment, garnered it an international reputation as the "Centre of Learning".