Ubaydallah ibn Muhammad al-Mahdi (Arabic: عبيد الله بن محمد المهدي, romanized: ʿUbayd Allāh ibn Muḥammad al-Mahdī)[1] (771–810/11) was an Abbasid prince.
[2] In 761, the future caliph al-Mahdi married Raytah as his first wife after his return from Khurasan.
[3] During the reign of his half-brother Harun al-Rashid (r. 786–809), Ubaydallah was appointed as governor of Arminiyah and the northwestern provinces in 788/9, succeeding Yazid ibn Mazyad al-Shaybani.
[7] Ubaydallah was contemporary and related to several Abbasid caliphs, princes and princesses.
He had total ten half-siblings and he had one full brother named Ali ibn Muhammad al-Mahdi.