The SS Rex was an Italian ocean liner launched in 1931. She held the westbound Blue Riband between 1933 and 1935. Originally built for the Navigazione Generale Italiana (NGI) as the SS Guglielmo Marconi, its state-ordered merger with the Lloyd Sabaudo line meant that the ship sailed for the newly created Italian Line.
Rex operated transatlantic crossings from Italy with its running mate, Conte di Savoia. On 8 September 1944, off Koper, Rex was hit by 123 rockets launched by RAF aircraft, caught fire from stem to stern, rolled onto the port side, and sank in shallow water. The ship was broken up at the site beginning in 1947.