Over the course of the late nineteenth and early twentieth centuries, Muslim modernist thinkers and writers in South Asia demanded a reconciliation between Islam and European thought in response to a perceived crisis of Islam. In the ensuing modernist movements, newly founded voluntary associations and their lay members played a crucial role in popularizing and disseminating modernist ideas on the ground, transforming definitions of both religious identity and community in the process. Through an in-depth and multifaceted historical analysis of one of the foremost Muslim associations of colonial North India, the Society for the Defence of Islam (Anjuman-i Himayat-i Islam, established 1884 in Lahore), Maria-Magdalena Pruss proposes a nuanced understanding of Islamic modernism as a mode of thought, highlighting its internal diversity and complex development over a period of more than sixty years. The evolution of this influential association reveals the role and work of lay people, who are shown to be a highly active force in defining and redefining Muslim religious identity through social and educational reform, community welfare initiatives, polemical and apologetic publications, and debates – both within and outside the Muslim community – as well as anti-colonial and nationalist activism. Turning the spotlight away from religious scholars and drawing from extensive, previously untapped local archives and vernacular source materials, Rethinking Islamic Modernism uncovers alternative and localized genealogies of Islamic modernism and makes a compelling argument for taking modernism seriously as a religious tradition in its own right.