Al-Mustansir may refer to:
- Ma'ad al-Mustansir Billah (1029–1094), eighth Fatimid Caliph
- Sayf al-Dawla ibn Hud al-Mustansir (r. 1145–1146), Muslim ruler of Valencia and Murcia
- Al-Mustansir (caliph) (المستنصر بالله) (died 1242), penultimate Abbasid Caliph in Baghdad from 1226 to 1242
- Al-Mustansir II of Cairo, Abbasid Caliph for the Mamluk Sultans between 1261 and 1262
- Abu 'Abd Allah (r. 1249-1277), Hafsid ruler of North Africa and self-declared Caliph, whose honorific surname was Al-Mustansir