Abū Jaʿfar ʿAbd Allāh ibn Muḥammad al-Manṣūr (/ælmænˈsʊər/; Arabic: أبو جعفر عبد الله بن محمد المنصور‎; 95 AH – 158 AH (714 CE – 6 October 775 CE) usually known simply as by his laqab Al-Manṣūr (المنصور) was the second Abbasid caliph, reigning from 136 AH to 158 AH (754 CE – 775 CE) succeeding his brother al-Saffah (r. 750–754). He is known for founding the 'Round City' of Madinat al-Salam, which was to become the core of imperial Baghdad.