Izz ad-Din Abd al-Qadar ibn Mustafa ibn Yusuf ibn Muhammad al-Qassam (1881 or 19 December 1882 – 20 November 1935) (Arabic: عز الدين بن عبد القادر بن مصطفى بن يوسف بن محمد القسام / ALA-LC: ʿIzz ad-Dīn ibn Abd al-Qāder ibn Mustafa ibn Yūsuf ibn Muhammad al-Qassām) was a Syrian Muslim preacher, and a leader in the local struggles against British and French Mandatory rule in the Levant, and a militant opponent of Zionism in the 1920s and 1930s.

Al-Qassam studied at Al-Azhar University in Egypt and afterward became an Islamic revivalist preacher in his hometown of Jableh in Syria during the last years of Ottoman rule. Following his return, he became an active supporter of the Libyan resistance to Italian rule, raising funds and fighters to aid the Libyans and penning an anthem for them. He would later lead his own group of rebels in alliance with Ibrahim Hananu to fight against French Mandatory forces in northern Syria in 1919–20.

Following the rebels' defeat, he immigrated to Palestine, where he became a Muslim waqf (religious endowments) official and grew incensed at the plight of Palestinian Arab peasants. In the 1930s, he formed bands of local fighters and launched attacks against British and Jewish targets. He was eventually killed in a manhunt following his alleged role in the killing of a British policeman. Israeli historian Tom Segev has called him 'the Arab Joseph Trumpeldor'. His campaign and death were factors that led to the 1936–1939 Arab revolt in Palestine.