Caio Duilio was an Italian Caio Duilio class battleship that served Regia Marina during World War I and World War II.

Built as a 29,861 t battleship with 10 12.6 guns, she and her sister Andrea Doria went with several changes in their career including receiving seaplanes. Modernisation between 1937 and 1940 turned both ships into new ones.

Caio Duilio was damaged by a torpedo during the Battle of Taranto. She was towed to Genoa for repairs in 6 months, and narrowly escaped further damage when the port was bombarded by British warship in February 1941. She was placed on the reserve in 1942. After the surrender to the Allies in 1943, Caio Duilio was used as a training ship. Finally the 41-year-old draednought, now old and worn, was scrapped at La Spezia in 1957.