This article explores the ideological relationship between free market capitalism and Islamism. While existing studies have attended to Islam’s engagement with capitalism, less attention has been given to the ideological intimacy of this relationship and, in particular, the increasing presence of radical free market thought in global Islamist politics, or what I have termed ‘libertarian Islamism’. The dominant narrative of Islamism, thus, constricts our understanding of the wider ideological ecology at play in the global political mobilization of Islam. While political Islam is often regarded as being rooted in a broadly leftist intellectual milieu, it has rather encapsulated variant conceptions of liberty, both left and right, and is currently undergoing what one might term a ‘free-market turn’. Within this milieu, a distinctly radical, anti-statist libertarian ideology has also emerged with an intimate relationship to conservative libertarian activists in the West. The presence of libertarian Islamism serves to recalibrate dominant understandings of ‘radical’ Islam and its purportedly fractious ideological relationship with the West.