Al-Mamun of Toledo

Yahya ibn Ismail al-Mamun or Yahya ben Ismael ben-Dylinun (died 1075) was a member of the Banu Dil-Nun dynasty who was king of the Taifa of Toledo between 1043 and 1075.

In 1062 he promised his allegiance to king Ferdinand I of León and Castile a fact that did not prevent him from giving military support to his son-in-law Abd al-Aziz ibn Amir, king of the Taifa of Valencia, when the Castilian king laid siege to the city. When Ferdinand I saw himself forced to end the siege and remove his army, Al-Mamun agreed to a union with the Taifa of Valencia which was to form a part of the Toledo taifa until 1092. He died at Córdoba in 1075.