The Oxford Handbook of the Pelagian Controversy delves into the heart of one of Christianity's earliest and most profound theological disputes. The Pelagian controversy, characterized by fierce debates on topics such as original sin, grace, and predestination, was a pivotal moment in the development of Christian doctrine during the early fifth century, unfolding across continents and involving influential figures like Augustine of Hippo, Pelagius, Caelestius, and Julian of Aeclanum. Beyond a mere theological and ecclesiastical debate, Pelagianism was an historical event which had far-reaching consequences, even influencing imperial decisions, and shaping later evolutions in the West -- theologically, philosophically, but also politically and historically. While shedding light on the historical intricacies of the Pelagian controversy, this Handbook also explores its enduring legacy. The discussions surrounding human autonomy, sexuality, and human limitations continue to shape contemporary theological and ethical discussions. With a strong emphasis on methodological precision, this comprehensive volume offers a balanced view of the Pelagian controversy, avoiding oversimplification, highlighting the importance of lost sources and the contributions of lesser-known figures, and uncovering the reception history of the controversy through the centuries. This Handbook is an indispensable resource for scholars and students interested in the history of the West and of Christianity, particularly concerning the profound philosophical and theological questions that continue to influence our modern culture.