Al-Mustansir Bi'llah (full name:Abû Ja`far al-Mustansir bi-llah al-Mansûr ben az-Zâhir Surname Al-Mustansir) was the Abbasid Caliph in Baghdad from 1226 to 1242.
He succeeded Caliph Az-Zahir in the year 1226.
Al-Mustansir was born in Baghdad on 1192.
On his father's death in 1226 he has succeeded his father Az-Zahir as the thirty-sixth Abbasid Caliph.
Al-Mustansir died on 5 December 1242.
His son Al-Musta'sim succeeded him as the thirty-seventh Caliph of the Abbasid Caliphate.
Mustansiriya Madrasah, was established in 1227 (or 1232/34 A.D.
by some accounts) by the Abbasid Caliph Al-Mustansir and is one of the oldest universities in the world.
Its building, located on the left bank of the Tigris River, survived the Mongol invasion and has been restored.