G. K. Chesterton’s anti-Semitism has attracted much scholarly attention, but his views on Islam have largely passed without comment. This article situates Chesterton’s writings in relation to historical views of Islam in Britain and the political, cultural and religious context of the early twentieth century. Chesterton’s complex and contradictory opinions fail to support easy conclusions about the immutability of prejudice across time. His views of Islam are at times orientalist and at other times critical of imperialism and elitism. As well as drawing on medieval Catholic ideas about the “heresy” of Islam, Chesterton also links Islam with Protestant Christianity. From another perspective, his views of Islam draw on liberal traditions of humanitarian interventionism and democratic patriotism. Finally, he also used Islam as a symbol of a corroding modernity. This study suggests the need for a historically sensitive genealogy of the evolution of anti-Muslim prejudice which is not predetermined by the politics of the early twenty-first century.