Caio Duilio was an Italian Andrea Doria-class battleship that served in the Regia Marina during World War I and World War II. She was named after the Roman fleet commander Gaius Duilius. Caio Duilio was laid down in February 1912, launched in April 1913, and completed in May 1916. She was initially armed with a main battery of thirteen 305 mm (12.0 in) guns, but a major reconstruction in the late 1930s replaced these with ten 320 mm (13 in) guns. Caio Duilio saw no action during World War I owing to the inactivity of the Austro-Hungarian fleet during the conflict. She cruised the Mediterranean in the 1920s and was involved in the Corfu incident in 1923.