Yahya al-Mu`tasim (Arabic: ? ; Ab? Zakar?y?' Al-Mu`ta?im Ya?y? ibn An-Nir; died 1236) was an Almohad rival caliph who reigned from 1227 to 1229. He was a son of Muhammad al-Nasir and brother of Yusuf II, Almohad caliph.
At the death of his uncle Abdallah al-Adil, Yahya was supported by the sheikhs of Marrakesh, but two years later he was turned down by another pretender, his other uncle Idris al-Ma'mun. At the latter's death in 1232, Yahya renewed his pretenses, but his cousin Abd al-Wahid II was preferred to him. He was anyway able to keep Marrakesh until his death in 1236, after which the Almohad territories were again united under Abd al-Wahid.