Ali ibn Musa ( Larabci : علي ابن موسى), wanda kuma aka fi sani da lakabinsa Ar-Ridha (wanda aka yarda da shi), shi ne Imami na Shi'a na takwas, bayan mahaifinsa Musa al-Kadhim, da kuma gaban ɗansa Muhammad al-Jawad . Ya kasance Limamin Ilimi bisa ga mazhabar Shi'a ta Zaydi (Fiver) da Sufaye . Ya rayu a zamanin da khalifofin Abbasiyyawa ke fuskantar matsaloli da yawa, mafi mahimmanci daga cikinsu shi ne tawayen Shi'a. Halifa Al-Mamun ya yi kokarin gyara wannan matsalar ta hanyar nada Al-Ridha a matsayin khalifa na gaba, duk da haka, a mahangar Shi'a, lokacin da Al-Ma'mun ya ga cewa Imam ya kara samun farin jini, sai ya yanke shawarar gyara kuskurensa ta guba shi. An binne Imam a wani ƙauye a Khorasan, wanda daga baya ya sami sunan Mashhad, ma'ana wurin shahada. A yau haramin Imam Reza da ke Mashhad ya mamaye yanki mai girman murabba'in mita 598,657 (kadada 147.931). Ana danganta ayyukan bin shi.