Sheikh Izz ad-Din al-Qassam (1882-1935) (Arabic: عزّ الدين القسّام) was born in Latakia, Syria and immigrated to the British Mandate of Palestine. Qassam was a militant Sufi preacher who rejected the moderate approach towards the British taken by the Mufti of Jerusalem, Amin al-Husayni, and the Supreme Muslim Council . When the Mufti rejected his plans to divert funding for mosque repairs towards the purchase weaponry, Qassam found support in the Arab Nationalist Istiqlal movement. Qassam continued to attempt an alliance with the Mufti in order to attack the British but failed as the Mufti was still committed to a diplomatic approach at the time. Qassam went ahead with his plans to attack the British on his own and was soon killed in 1935.

Today, Hamas named its military divisions by his name. The Qassam rocket is named after the brigades who use them.