With a loss of around 9400, making it the worst maritime disaster in human history, German passenger ship The Wilhelm Gustloff sunk on January 30, 1945. An estimated 9,400 passengers and crew, fleeing East Prussia, perished (5,000 children) as a result of the the sinking of MS Wilhelm Gustloff. Gustloff was carrying 10,000 refugees packed into every corner of the ship. Struck by three Soviet torpedoes, she took only 70 minutes to sink.

The Wilhelm Gustloff was the first purpose-built cruise liner for the Nazi Kraft durch Freude (KdF) (Strength Through Joy) labor organization. The ship was named after Wilhelm Gustloff, the assassinated German leader of the Swiss Nazi party. The purpose was to provide recreational and cultural activities for German functionaries and workers, including concerts, cruises, and other holidays. The Wilhelm Gustloff was the flagship of the KdF cruise fleet until the spring of 1939. That was her last civilian role. From then on she served the needs of the German military.

From September 1939 to November 1940, she served as a hospital ship. On her first mission to the Baltic Sea, she treated 650 wounded Polish soldiers. Beginning November 20, 1940, the medical equipment was removed from the ship and it was repainted from the hospital ship colours of white and green to standard naval grey.

The ship's final voyage was to evacuate civilians, Kriegsmarine sailors, and wounded German soldiers from Gotenhafen to Kiel. The ship's complement and passenger lists totaled 6,050 people on board, but this did not include many refugees who boarded the ship without being recorded in the ship's official embarkation records. Heinz Schön, who carried out extensive research into the sinking during the 1980s and 1990s, concluded that the Wilhelm Gustloff was carrying a crew of 173 (naval armed forces auxiliaries), 918 officers, NCOs, and men of the 2nd Submarine Training Division (2. Unterseeboot-Lehrdivision), 373 female naval auxiliary helpers, 162 badly wounded soldiers, and 8,956 refugees, for a total of 10,582 passengers and crew (even though the ship was only built for 1,465 passengers).

The ship had four captains on board, who couldn't agree on the best best course of action to guard against submarine attacks. Rhe senior civilian captain, Friedrich Petersen, decided to head for deep water. When he was informed by radio of an oncoming German minesweeper convoy, he decided to activate his ship's red and green navigation lights so as to avoid a collision in the dark, making the Wilhelm Gustloff easy to spot in the night. The ship was soon sighted by the S-13 which fired three torpedoes at the Wilhelm Gustloff's port side about 30 km (20 miles) offshore between Großendorf and Leba soon after 9:00pm.
In the panic that followed, many of the refugees were trampled in the rush to the lifeboats and life jackets. Some equipment was lost as a result of the panic. The water temperature in the Baltic Sea at this time of year is usually around 4°C; however, this was a particularly cold day, with an air temperature of -10° to -18°C and ice floes covering the surface. Many deaths were either caused directly by the torpedoes or by instant drowning in the onrushing water. Others were crushed in the ensuing panic on the stairs and decks, and many jumped into the icy, dark Baltic. Reports talk about children clinging onto adults and women trying to save their babies, though constant waves dragged them away from them, most never to be seen again. Small children fitted with life jackets for adults drowned because their heads were under water while their legs were in the air.