This article examines the theology of Katherine Parr, sixth and surviving wife of Henry VIII, through a close reading of her mature work, The Lamentation of a Sinner. In particular, I treat Parr’s theological use of the epistle to the Romans to inform and structure her doctrine of the work of Christ within The Lamentation. I argue that Parr follows the structure of Romans in her opening lament over sin, her central discussion of the cross of Christ, and her application of this theology to the Christian lives of the people of England’s church. I also posit Parr’s use of several overlapping motifs for Christ’s work within The Lamentation’s treatment of the atonement and its relationship to the Protestant understanding of justification by faith.