Type U 57 was a class of U-boats built during World War I by the Kaiserliche Marine. Six Type U 57 were ordered at the beginning of the war and these were commissioned in 1916. A further six were ordered in 1915 and commissioned in 1917. Seven were lost during the war and the remaining five surrendered to the Allies and were scrapped.
When World War I broke out on 28 July 1914, the German Navy initiated an emergency war building program, the so-called mobilisation program. This mobilisation program called for the immediate construction of seventeen U-boats by the two submarine building shipyard in Germany: the Germaniawerft in Kiel and the Kaiserliche Werft Danzig. The Kaiserliche Werft received an order for five Type U 43 U-boats and the Germaniawerft would have received an order for the remaining twelve U-boats, but since this yard experienced serious delays in the delivery of the previous order of eleven Type U 31 U-boats, only six Type U 51 U-boats were ordered from Germaniawerft on 23 August 1914 and the remaining six were ordered as Type U 57 from a new yard AG Weser.
When in August 1915 AG Weser had capacity to build extra U-boats, six more Mobilisation U-boats - were ordered from AG Weser based on the same Type U 57 design.
The first three U 57s were fitted with two MAN six-cylinder two-stroke 8SS35 diesel engines with a total of t for use on the surface, the other nine Type U 57 U-boats were fitted with two more powerful S6V45/42 MAN diesel engines with a total of . All Type U 57 had two Siemens-Schuckert double-acting electric motors with a total of for underwater propulsion. These engines powered two shafts. Constructional diving depth was .
All twelve Type U 57 U-boats were armed with four torpedo tubes, two fitted in the bow and two in the stern. U-57 - U-62 carried seven torpedoes and U-99 - U-104 carried ten to twelve torpedoes. Most boats received initially one or two SK L/30 deck guns. Some boats had one 8.8 cm deck gun replaced with a SK L/45 gun. The boats' complement was four officers and thirty-two enlisted men.