Ali ibn Musa al-Rida (Arabic: ?????? ???? ??????? ?????????, Aliy Musa ar-Ri?a; c.
29 December 766 – 23 August 818)), also spelled Reza in Persian, also known as Abu al-Hasan, was a descendant of the Islamic prophet, Muhammad, and the eighth Shia Imam, after his father Musa al-Kadhim, and before his son Muhammad al-Jawad.
He was an Imam of knowledge according to the Zaydi (Fiver) Shia school and Sufis.
He lived in a period when Abbasid caliphs were facing numerous difficulties, the most important of which was Shia revolts.
The Caliph Al-Ma'mun sought out a remedy for this problem by appointing Al-Ridha as his successor, through whom he could be involved in worldly affairs.
However, according to the Shia view, when Al-Ma'mun saw that the Imam gained even more popularity, he decided to correct his mistake by poisoning him.
The Imam was buried at the Imam Reza shrine in a village in Khorasan, which afterwards gained the name Mashhad, meaning the place of martyrdom.