Muhammad I al-Mustansir (Abd Allah Muhammad I al-Mustansir ben Yahya I) (1228-1277) is the second ruler of the Hafsid dynasty in Ifriqiya and the first to claim the title of Khalif.

Al-Mustansir concludes a peace agreement to end the Eighth Crusade launched by Louis IX, King of France, in 1270.

Muhammad I al-Mustansir had been a vassal of the Kingdom of Sicily, but had shaken off his allegiance when King Manfred of Sicily was overthrown by Charles I of Naples.