Barra do Piraí (Portuguese pronunciation: [ˈbaʁɐ du piɾɐˈi]) is a municipality of the Brazilian state of Rio de Janeiro. It is located at latitude 22º28'12" South and longitude 43º49'32" East. Its population is 100,764 (2020) and its area is 578.471 km². It is 114 km from Rio de Janeiro.

The municipality contains part of the 5,952 hectares (14,710 acres) Serra da Concórdia State Park, created in 2002.