Caio Duilio (C 554) was an Andrea Doria-class helicopter cruiser serving in the Marina Militare. Constructed by Navalmeccanica in Castellammare di Stabia, the vessel was laid down on 16 May 1958, launched on 22 December 1962, and officially commissioned into service on 30 November 1964. Named after the Roman consul Gaius Duilius, the ship was designed primarily for long-range anti-aircraft and anti-submarine defense. The cruiser featured a distinctive hull equipped with a large helicopter deck and hangar located at the stern, initially intended to carry three Sea King helicopters; however, these proved too large, leading to the deployment of four Agusta-Bell AB-212 helicopters instead. Its armament included a single Mark 10 twin rail launcher for American Terrier surface-to-air missiles positioned at the bow, providing substantial air defense capability. Close-in anti-aircraft protection was assured by eight 76mm/L62 Allargato rapid-fire guns mounted around the superstructure. For anti-submarine warfare, Caio Duilio was equipped with two sets of triple torpedo tubes for lightweight anti-submarine torpedoes. The vessel was assigned to the 2nd High Seas Naval Group of the II Divisione Navale, based in Taranto, later transferring to La Spezia in the 1980s. During the late 1970s, the ship underwent significant upgrades, including the installation of the more advanced SM-1ER Standard missile, along with improved radar and sonar systems. Between 1979 and 1980, Caio Duilio was converted into a training cruiser to replace the older San Giorgio. Its original hangar was repurposed as classrooms and accommodation facilities, while a smaller, new hangar was added at the bow, reducing its helicopter capacity to two. Additionally, the aft two 76mm guns and their fire control radars were removed. Caio Duilio was decommissioned on 15 December 1989, struck from the naval register on 19 July 1991, and sold for scrap on 31 December 1992. Her service marked a notable period of Italy's naval development, integrating helicopter capabilities with missile technology for fleet defense.

This description has been generated using GPT-4.1-NANO based on the Vessel's wikidata information and then modified by ShipIndex.org staff.