SM UC-57

SM UC-57 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (Kaiserliche Marine) during World War I. The U-boat was ordered on 12 January 1916, laid down on 14 March 1916, and was launched on 7 September 1916. She was commissioned into the German Imperial Navy on 22 January 1917 as SM UC-57. In 7 patrols UC-57 was credited with sinking 5 ships, either by torpedo or by mines laid.

UC-57 disappeared in 1917 after landing a party of Finnish Jägers and 4 tons of munitions on the island of Hamnskär, circa 30 km from Loviisa, on 18 November. UC-57 was going to remain on the seabed overnight and then return to Germany but never arrived. She was probably sunk by a Russian mine.