This thesis presents a study of a newly discovered and previously unstudied painting of St. Catherine of Siena by Rutilio Manetti (1620s-1630s), which features a seemingly unique iconography. Based on the fifteenth-century hagiographic accounts, it identifies the subject matter and properly retitles the work, St. Catherine of Siena Drinking from the Side Wound of Christ . Contextualizing the work within its historical moment, this thesis shows that the artist navigates post-Tridentine rules of decorum in creating an image which celebrates women’s religious tradition and reasserts their spiritual authority during a time in which such traditions and authority were discouraged by the Catholic Church. Representing a new depiction of St. Catherine at the time, the painting furthermore instructively demonstrates to its viewer what a mystical vision centered upon an art object (the crucifix) should look like. It highlights the somatic spirituality particularly associated with religious women, which points to a patron who championed that tradition. Evidence from hagiographies, iconographic and religious studies, and primary and secondary texts on the Council of Trent’s decrees are brought to bear on this unusual painting, exploring themes such as asceticism, eroticism, and Eucharistic devotion. This thesis contributes to the study of the study of iconography of St. Catherine of Siena and other female mystic religious figures, especially in the context of the post-Tridentine era. Building on previous work on women’s religious studies and post-Tridentine art, this thesis further elucidates the relationship between doctrine, religious practice, gender, and art at that historic juncture.