Enrico Toti was one of four Balilla-class submarines built for the Regia Marina during the late 1920s. The boat played a minor role in the Spanish Civil War of 1936–1939 supporting the Spanish Nationalists. She was the only Italian submarine to have sunk a Royal Navy submarine during the Second World War.
The Glauco class was a pair of submarines ordered by the Portuguese government, but were taken over and completed for the Regia Marina during the 1930s. They played a minor role in the Spanish Civil War of 1936–1939 supporting the Spanish Nationalists.
The Foca class were a group of three minelaying submarines built for the Regia Marina during the 1930s. All three sister ships played minor roles during the Second World War. One was lost to unknown causes while trying to lay a minefield off British Palestine in 1940, but the other two survived the war to be discarded in 1947.
Delfino was one of four Squalo-class submarines built for the Regia Marina during the late 1920s. The boat served in World War II and was sunk in 1943 after a collision with another Italian ship.
The Squalo-class submarines were a group of four submarines built for the Royal Italian Navy during the 1930s. They were built at the Cantieri Riuniti dell'Adriatico (CRDA) shipyard at Monfalcone, and designed by Curio Bernardis.
Glauco was the lead ship of her class of two submarines ordered by the Portuguese government, but taken over and completed for the Regia Marina during the 1930s.
Otraria was one of two Argo-class submarines ordered by the Portuguese government, but taken over and completed for the Regia Marina during the 1930s. She played a minor role in the Spanish Civil War of 1936–1939 supporting the Spanish Nationalists.
Domenico Millelire was one of four Balilla-class submarines built for the Regia Marina during the late 1920s.
Balilla was the lead ship of her class of four submarines built for the Regia Marina during the late 1920s.
Foca was the lead ship of her class of three submarine minelayers built for the Regia Marina during the late 1930s.
Atropo was one of three Foca-class submarine minelayers built for the Regia Marina during the late 1930s.
Zoea was one of three Foca-class submarine minelayers built for the Regia Marina during the late 1930s.
The Settembrini class was a pair of submarines built for the Regia Marina during the late 1920s. They played a minor role in the Spanish Civil War of 1936–1939 supporting the Spanish Nationalists.
The Pisani-class submarines were built for the Regia Marina during the late 1920s. They played a minor role in the Spanish Civil War of 1936–1939 supporting the Spanish Nationalists.
Squalo was the lead ship of her class of four submarines built for the Regia Marina during the late 1920s. The boat served in World War II and was decommissioned in 1948.
Tricheco was one of four Squalo-class submarines built for the Regia Marina during the late 1920s. The boat served in World War II and was sunk in 1942 by the British submarine HMS Upholder.
The Bragadin-class submarines were built for the Regia Marina during the late 1920s. Both boats participated in the Second World War and were discarded in 1948.
Marcantonio Bragadin was the lead ship of her class of two submarines built for the Regia Marina during the late 1920s. The boats participated in the Second World War and was discarded in 1948.
Filippo Corridoni was one of two Bragadin-class submarines built for the Regia Marina during the late 1920s. The boat participated in the Second World War and was discarded in 1948.
Narvalo was one of five Glauco-class submarines built for the Regia Marina during the early 1900s. The boat served in World War I with defensive purposes and was demolished in 1918.
Italy 
