The SS Rex was an Italian ocean liner launched in 1931. It held the westbound Blue Riband between 1933 and 1935. Originally built for the Navigazione Generale Italiana as the SS Guglielmo Marconi, its state-ordered merger with the Lloyd Sabaudo line meant that the ship sailed for the newly created Italia Flotta Riunite.
On May 12, 1938, in a demonstration of U.S. air power, three YB-17 bombers of the U.S. Army Air Corps intercepted the Rex 620 miles at sea in a highly publicized event. The Rex operated transatlantic crossings from Italy with its running mate, the 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. She burned for four days, then rolled onto the port side, and sank in shallow water. The ship was broken up at the site beginning in 1947.