Abu'l-Faḍl Ibn al-Khashshāb (أبوالفضل بن الخشاب; died 1125) was the Shi'i qadi and ra'is of Aleppo during the rule of the Seljuk emir Radwan.
His family, the Banu-l-Khashshab, were wealthy wood-merchants in the city. Upon the arrival of the First Crusade, ibn al-Khashshab was one of the first to preach jihad against the crusaders, a concept which became more popular throughout the 12th century. His preaching was popular among the masses, but Radwan, along with his Hashshashin advisors, were not willing to wage battle against the newly formed crusader states. Aleppo was continually threatened by the crusaders and eventually Radwan was humiliated by Tancred of Antioch, forced to place crosses on the minarets of some of the mosques in the city.
Ibn al-Khashshab had sought help from the Abbasid caliph in Baghdad, but each time his requests were ignored; finally, in 1111, he travelled to Baghdad to seek help from the caliph in person. He instigated a riot and destroyed the pulpit of the minbar in the private mosques of the Seljuk sultan and the caliph. In response, the sultan ordered Mawdud, the governor of Mosul, to come to Aleppo's aid, and ibn al-Khashshab returned home. However, Radwan did not want Mawdud interfering in his affairs, and had ibn al-Khashshab imprisoned; Mawdud and Radwan could not cooperate and Mawdud returned home.
When Radwan died in 1113, ibn al-Khashshab governed the city in place of weak or child emirs. He rid the city of the Hashshashin, by expulsion or execution. When the crusaders threatened the city again in 1119, Ibn al-Khashshab negotiated an alliance with Ilghazi of the Artuqid dynasty in Mesopotamia, and the crusader Principality of Antioch was defeated at the Battle of Ager Sanguinis that year. Ibn al-Khashshab personally led Aleppan troops in the battle.
The crusaders besieged Aleppo in 1124, and when they desecrated Muslim cemeteries outside the city, ibn al-Khashshab ordered that four of the six Christian churches in the city, including the cathedral, be converted into mosques. The besiegers, led by Baldwin II of Jerusalem and Joscelin I of Edessa, were allied with the Muslim Dubais, whom ibn al-Khashshab publicly denounced. The siege was eventually raised with help from Mosul in 1125, but later that year, ibn al-Khashshab was murdered by his old Hashshashin enemies. The next year Aleppo fell under the control of Zengi, who began to implement the jihad that ibn al-Khashshab had so fervently preached.
Another ibn al-Khashshab was the leader of the Shi'i in Aleppo during the time of Saladin. He wrote a four-volume annotated commentary of Al-Muqtassid, a grammar manual by Ibn Hubayrah, and commented on the Sermon of the roar of a camel. He was executed by As-Salih Ismail al-Malik in 1172.