Social anthropology was at the forefront of debates about culture, society, and economic development in the British Empire. This book explores the discipline's rise in the interwar period, crisis amid decolonization, and ironic reemergence in the postwar metropole. Across the humanities and social sciences, activists and scholars used anthropological concepts forged in empire to rethink British society at midcentury. Participant Observers shows how colonial anthropology helped define the social imagination of postimperial Britain. Part institutional history of the discipline's formation, part cultural history of its impact, this is the first account of social anthropology's pivotal role in Britain's intellectual culture.