This dissertation offers an analysis of Matthias Joseph Scheeben's theology of deification by demonstrating the connection between his trinitarian theology and theology of grace. Chapter 1 ("Mysteric-Supernatural Deification: A Doctrine Emerges") argues that Scheeben's theology of deification, with its characteristic accents on mystery and the supernatural, emerged as a counterproposal to the theological rationalism Scheeben saw threatening Christian life and theology in nineteenth-century Germany. Chapter 2 ("The Divine Trinity: Fons Vitae") shows how the distinctive accents of Scheeben's emanational trinitarian theology (e.g., a strong use of the psychological analogy, a robust doctrine of personhood, and a linear ex Patre per Filium trinitarian arrangement) relate to Scheeben's theology de Deo uno and anticipate his doctrine of grace by foregrounding the concept of divine self-communication. Chapter 3 ("Grace: Becoming God's Adopted Children") analyzes Scheeben's theology of the divine missions, conception of the relation of nature and grace, and theology of human union with God understood as trinitarian deification, through which we become children of the Father, spouses of the Son, and temples of the Holy Spirit.