SS Principe Umberto was an Italian passenger and refrigerated cargo ship built in 1908 for Navigazione Generale Italiana. During World War I, Principe Umberto served as an armed merchant cruiser. While transporting troops in the Adriatic in June 1916, the ship was sunk by Austro-Hungarian U-boat U-5 with the loss of 1,926 men.It was the worst naval disaster of World War I in terms of human lives lost.