Abu'l-Faḍl Ibn al-Khashshāb (أبوالفضل بن الخشاب; died 1125) was the Shi'i qadi and rais 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.