Jacopo Passavanti: The Mirror of True Penitence presents a complete English translation of Jacopo Passavanti’s unfinished summa on penitence – an essential yet often overlooked work of 14th-century religious thought. Based on his 1354 Lenten sermons at the church of Santa Maria Novella in Florence, this book organizes and expands Passavanti’s teachings into a structured guide on sin, confession, and repentance, making them accessible beyond the fleeting moment of oral delivery. Written in vernacular Italian rather than Latin, this work reflects the growing importance of Tuscan as a literary and intellectual language, placing Passavanti among the key figures shaping Florence’s cultural evolution. His clear, engaging prose blends medieval Scholasticicism with vivid storytelling, using historical references and familiar exempla to illustrate moral teachings. A crucial addition to medieval studies, this translation brings Passavanti’s voice to modern readers, illuminating a pivotal moment in Florence’s spiritual and cultural history.