This dissertation explores the central role of Leiblichkeit (“bodiliness”) in the theology of Karl Rahner (1904–1984), arguing that bodiliness functions as a foundational key across his entire theological corpus. While secondary scholarship has acknowledged the concrete and historical dimensions of human experience, it has largely overlooked Leiblichkeit as a distinct theological category. This study addresses that gap by showing that bodiliness provides a unifying hermeneutical framework for interpreting Rahner’s reflections on spirituality, philosophy, grace, Christology, anthropology, ecclesiology, and eschatology. The dissertation is divided into two parts: the first examines the spiritual and philosophical dimensions of bodiliness as the ground of mystical experience and human knowledge; the second explores its theological implications, demonstrating how Rahner’s thought is intrinsically grounded in historicity and human embodiment. The central claim is that bodiliness functions as a leitmotif in Rahner’s theology—an existential medium of relationality and encounter with being in the world. By reclaiming the significance of bodiliness, this study deepens the interpretation of Rahner’s theology and opens new avenues for dialogue with the human sciences, including bioethics, feminist theory, ecological theology, psychology, artificial intelligence (AI), and philosophical anthropology