Operation Deadlight was the code name for the scuttling of U-boats surrendered to the Allies after the defeat of Germany near the end of World War II.

Of the 154 U-boats surrendered, 121 were scuttled in deep water off Lisahally, Northern Ireland or Loch Ryan, Scotland in late 1945 and early 1946. On February 12, 1946 at 10:04am, U 3514 received the dubious honor of being the last U-boat sunk by Operation Deadlight. The other 33 were used for various tasks and then sunk; e.g., U 1105 , sunk on explosives trial in the Potomac in 1948.

The British Ministry of Defense has awarded a salvage contract to a firm that plans to raise most, if not all, of the U-boats scuttled under Operation Deadlight. This is presumably because the submarines contain metals valuable enough to warrant their salvage.

Several U-boats survived Operation Deadlight. Some were claimed as prizes by Britain, Norway and the Soviet Union. Five were in the far east when Germany surrendered and were commandeered by Japan. Two U-boats that survived Operation Deadlight are museum ships today. U 505 was slated for scuttling but Rear Admiral Daniel V. Gallery argued successfully that she did not fall under Operation Deadlight. United States Navy Task Group 22.3, under then-Captain Gallery, had captured U 505 in battle on 4 June 1944. Having been captured, not surrendered at the end of the war, she survived to become a war memorial at the Museum of Science and Industry in Chicago. U 995 was transferred to Norway by Britain in Oct 1948 and became the Norwegian Kaura. She was returned to Germany in 1965 to become a museum ship in 1971.