The Abbasid Caliphate or, more simply, the Abbasids (Arabic: العبّاسيّون / ISO 233: al-‘abbāsīyūn), was the third of the Islamic caliphates. It was ruled by the Abbasid dynasty of caliphs, who built their capital in Baghdad after overthrowing the Umayyad caliphate from all but the al-Andalus region.
The Abbasid caliphate was founded by the descendants of the Prophet Muhammad's youngest uncle, Abbas ibn Abd al-Muttalib (566-653), in Kufa in 750 CE and shifted its capital in 762 to Baghdad. Within 150 years of gaining control of Persia, the caliphs were forced to cede power to local dynastic emirs who only nominally acknowledged their authority. The caliphate also lost the Western provinces of al-Andalus, Maghreb and Ifriqiya to an Umayyad prince, the Aghlabids and the Fatimid Caliphate, respectively.
The Abbasids' rule was briefly ended for three years in 1258, when Hulagu Khan, the Mongol khan, sacked Baghdad, resuming in Mamluk Egypt in 1261, from where they continued to claim authority in religious matters until 1519, when power was formally transferred to the Ottoman Empire and the capital relocated to Constantinople.
Read more about Abbasid Caliphate: Rise, Power, Islamic Golden Age, Evolution of Islamic Identity, Fracture and Revival of Central Authority, Under The Mamluks, End of Dynasty, List of Abbasid Caliphs