The German theologian Dietrich Bonhoeffer understood Western civilization to be “approaching a completely religionless age” to which Christians must respond and adapt. This book explores Bonhoeffer’s own response to this challenge—his concept of a religionless Christianity—and its place in his broader theology. It does this, first, by situating the concept in a present-day Western socio-historical context. It then considers Bonhoeffer’s understanding and critique of religion, before examining the religionless Christianity of his final months in the light of his earlier Christ-centred theology. The place of mystery, paradox, and wholeness in Bonhoeffer’s thinking is also given careful attention, and non-religious interpretation is taken seriously as an ongoing task. The book aspires to present religionless Christianity as a lucid and persuasive contemporary theology; and does this always in the presence of the question which inspired Bonhoeffer’s theological journey from its academic beginnings to its very deliberately lived end—the question “Who is Jesus Christ?”