Endowed bathhouses constituted one of the principal revenue-generating categories of waqf properties in Iranian cities during the Qajar period. Beyond their hygienic function, they played a significant role in financing religious institutions, educational activities, and charitable services. Despite their historical importance, no independent study has systematically examined the endowed bathhouses of Sari on the basis of archival waqf deeds. This study analyzes the social background of the founders (waqifs), the spatial distribution of endowed bathhouses within the urban fabric of Sari, the economic structure of these endowments, and the functions of their revenues between 1251 and 1334 AH. Adopting a historical approach with a descriptive–analytical method, the research is based on data extracted from nine authenticated waqf deeds preserved in the Archives of the General Directorate of Endowments and Charitable Affairs of Mazandaran Province. The findings indicate that most endowed bathhouses were strategically located near bazaars, mosques, madrasas, and major communication routes, particularly around the Barforush Gate, to ensure sustainable revenues. Their founders included Qajar princes, landowners, local notables, merchants, and women, reflecting the broad social participation in the institution of waqf. The revenues were primarily allocated to Shi'i mourning ceremonies for Imam al-Husayn, while also supporting mosques, madrasas, religious students, the poor, orphans, pilgrims, the purchase of religious books, and the maintenance of religious buildings. Overall, the study demonstrates that endowed bathhouses formed an integral part of Sari's urban, economic, and religious organization during the Qajar period.