Guru to the World traces Vivekananda’s transformation from son of a Calcutta-based attorney into saffron-robed ascetic. At the 1893 World Parliament of Religions in Chicago, he fascinated audiences with teachings from Hinduism, Western esoteric spirituality, physics, and the sciences of the mind, in the process advocating a more inclusive conception of religion and expounding the evils of colonialism. Vivekananda won many disciples, most prominently the Irish activist Margaret Noble, who disseminated his ideas in the face of much disdain for the wisdom of a “subject race.” At home, he challenged the notion that religion was antithetical to nationalist goals, arguing that Hinduism was intimately connected with Indian identity. Ruth Harris offers an arresting biography, showing how Vivekananda’s thought spawned a global anticolonial movement and became a touchstone of Hindu nationalist politics a century after his death. The iconic monk emerges as a counterargument to Orientalist critiques, which interpret East-West interactions as primarily instances of Western borrowing. As Vivekananda demonstrates, we must not underestimate Eastern agency in the global circulation of ideas.