German submarine U-48 was a Type VIIB U-boat of Nazi Germany's Kriegsmarine during World War II, and the most successful that was commissioned. During her two years of active service, U-48 sank 51 ships for a total of 299,477 GRT and 1,060 tons; she also damaged four more for a total of 27,877 GRT over twelve war patrols conducted during the opening stages of the Battle of the Atlantic.

U-48 was built at the Germaniawerft in Kiel as yard number 583 during 1938 and 1939, being completed a few months before the outbreak of war in September 1939 and given to Kapitänleutnant (Kptlt.) Herbert Schultze. When war was declared, she was already in position in the North Atlantic, and received the news via radio, allowing her to operate immediately against Allied shipping.

GRT= Gross Register Tonnage
Name: U-48
Ordered: 21 November 1936[1]
Builder: Germaniawerft, Kiel
Cost 4,439,000 Reichsmark
Yard number: 583[1]
Laid down: 10 March 1937[1]
Launched: 8 March 1939[1]
Commissioned: 22 April 1939[1]
Decommissioned: October 1943
Victories:
50 merchant ships sunk
(299,477 GRT)
1 warship sunk
(1,060 tons)
4 merchant ships damaged
(27,877 GRT)