This study presents five little-known bathing chambers from the region of Amalfi in southern Italy. Dating from the thirteenth century, the baths define with remarkable consistency a type of structure that has not previously been identified or considered in histories of medieval architecture in the West. The study begins with an analysis of the five bathing chambers and their specific architectural features, technological remains, and domestic contexts. The diverse antecedents of the buildings, which appear in ancient Roman, medieval Italian, Byzantine, and Islamic architecture, are explored, along with the implications of this eclecticism for the history of southern Italy. Utilizing the rich array of surviving medieval documents for the region, including episcopal charters, royal decrees, and medical treatises, the study then reconstructs the economic, social, and scientific significance of the baths within medieval Amalfi. As monuments outside the traditional contexts of art production in southern Italy, the baths challenge long-standing characterizations of southern Italy's art and architecture, and point to the existence of a Mediterranean-wide balneal culture in which Byzantine, Islamic, and southern Italian communities participated.