Mahathir Mohamad's engagement with Islam remains one of the most understudied aspects of his six decades in the public limelight. Few students of late-twentieth-century Malaysian society have concerned themselves seriously with his pronouncements on what Islam was and, perhaps even more importantly, what Islam could do. This article argues that, while Mahathir's religious discourse had the transparently political objective of containing increasingly strident Islamist opposition, it was also a relatively coherent description of the type of religiosity and the religiously inspired personal qualities that a Malaysian Muslim should ideally possess. Even though the so-called ‘Islamization’ processes of the 1980s and 1990s have had some rather problematic consequences for Malaysian society as a whole, Mahathir's articulation of Islam's most fundamental spirit as a ‘theology of progress’ was in many aspects notably liberal and conducive to processes of democratization and civil society building. His emphasis on the pluralism and tolerance of Islamic civilization, as well as on Islam as a practical faith encouraging its adherents to prosperity and good neighbourliness, helped undergird official narratives of Malaysia as a harmonious, multi-cultural state.