This essay considers the role of the Virgin Mary in Sir Gawain and the Green Knight in light of Cistercian Marian devotional writing. Mary enters the poem as an image on Gawain’s shield, but Gawain’s focus on her recedes until she is all but forgotten at Bercilak’s castle. The study then examines the more structural role of the Virgin in the poem, specifically her invocation in two of the work’s dominant images: the star and the kiss. The star has long-standing Marian associations in the form of her title, maris stella. Less obviously, the kiss is connected to Mary through Song of Songs 1:1, “Osculetur me osculo oris sui.” Commentaries and sermons on this text by Bernard of Clairvaux and Aelred of Rievaulx, especially Aelred’s Sermon on the Nativity of Mary (XXIV), link these motifs and provide suggestive context for Sir Gawain.