In the fall of 2015, when the Palestinian Authority claimed that the State of Israel posed threats to the Al-Aqsa Mosque in Jerusalem, public attention in Israel turned again to Haj Amin al-Husseini, the former Grand Mufti of Jerusalem, a collaborator with Nazi Germany and the leader of Palestinian nationalism before and immediately after World War II. Some historians and, briefly, Israel’s Prime Minister also attributed to Husseini a significant decision-making role in the Holocaust in Europe. The following essay draws on scholarship on Holocaust decision-making in order to demonstrate that Husseini did not have an impact on Hitler’s decisions to murder the Jews of Europe. Rather his historical importance may be found in the texts of his speeches and essays of the 1930s and 1940s. They offer abundant evidence of his impact on Nazi Germany’s Arabic language propaganda aimed at North Africa and the Middle East during World War II and the Holocaust. Before, during and after his presence in Berlin from 1941 to 1945, Husseini played a central role in shaping the political tradition of Islamism by offering an interpretation of the religion of Islam as intrinsically anti-Semitic and anti-Zionist and in connecting that version to the anti-Semitic conspiracy theories of modern European history.