The Brin-class submarines were five Italian submarines that served in the Regia Marina during World War II. All ships were built by Tosi. Two boats were replacements for Archimede-class submarines secretly transferred to the Nationalists during the Spanish Civil War in 1937. The class were partially double hulled. The deck gun was initially mounted in the conning tower (to enable surface action during Indian ocean Monsoon). The gun was re-sited on the forward deck later in the war in surviving boats and the large conning tower was re-built to a smaller design.