What is the largest loss of life due to a ship sinking?

The Wilhelm Gustloff was torpedoed and sunk 30th January 1945 in the Baltic Sea with a loss of an estimated 9,400 people.

The ships final voyage was during Operation Hannibal in January 1945, when she was sunk while participating in the evacuation of civilian refugees, German soldiers, and U-boat personnel trapped by the Red Army in East Prussia. She was hit by three torpedoes from the Soviet submarine S-13 in the Baltic Sea on the night of January 30, 1945 and sank in under 45 minutes, taking an estimated 9,400 people with her. The sinking of the Wilhem Gustloff ranks as the largest known loss of life in a single sinking in maritime history.