Operation Teardrop was a United States Navy operation during World War II, conducted between April and May 1945, to sink German U-boats approaching the Eastern Seaboard that were believed to be armed with V-1 flying bombs. Germany had threatened to attack New York with V-1 flying bombs and rocket U-boats. After the war, it was determined the submarines had not been carrying either.

Operation Teardrop was planned during late 1944 in response to intelligence reports which indicated that Germany was preparing a force of missile-armed submarines. Two large U.S. Navy anti-submarine warfare task forces were set up. The plan was executed in April 1945 after several Type IX submarines put to sea from Norway bound for North America. While severe weather conditions in the North Atlantic Ocean greatly reduced the effectiveness of the four U.S. Navy escort carriers involved, long patrol lines of destroyer escorts detected and engaged most of the German submarines. Aircraft of the Royal Canadian Air Force supported this effort.

Five of the seven submarines in the group stationed off the United States were sunk, four with their entire crews. Thirty-three crew members from U-546 were captured, and specialists among them were interrogated under torture. One destroyer escort was sunk, USS Frederick C. Davis (DE-136), with the loss of most of her crew. The survivors were pulled from the water within three hours. The war ended shortly afterwards and all surviving U-boats surrendered. Interrogation of their crews found that missile launching equipment was never fitted to the U-boats, which was further confirmed after the war.

In late 1944, the Allies received intelligence reports which suggested that Germany's Kriegsmarine was planning to use V-1 flying bombs launched from submarines to attack cities on the east coast of the United States. In September of that year, Oskar Mantel, a spy captured by the U.S. Navy when the submarine (U-1229) transporting him to Maine was sunk, told his FBI interrogators that several missile-equipped U-boats were being readied. United States Tenth Fleet analysts subsequently examined photos of unusual mountings on U-boats at bases in Norway, but concluded that they were wooden tracks used to load torpedoes. Further rumors of missile-armed submarines emerged later that year, including one from Sweden passed on by the Supreme Headquarters Allied Expeditionary Force. The British Admiralty discounted these reports, and assessed that while V-1s could be potentially mounted on Type IX submarines, the Germans were unlikely to devote scarce resources to such a project.

Despite the Tenth Fleet and Admiralty assessments, the U.S. military and government remained concerned that Germany would conduct vengeance attacks against East Coast cities. In early November 1944, the Eastern Sea Frontier mounted an intensive search for submarines within 250 miles (400 km) of New York City. In late December 1944, the spies William Curtis Colepaugh and Erich Gimpel, who had been captured in New York City after being landed by U-1230 in Maine, told their interrogators that Germany was preparing a group of rocket-equipped submarines. On 10 December, the Mayor of New York City, Fiorello La Guardia, publicly warned that Germany was considering an attack on New York with long-range rockets. La Guardia's warning and the claims made by the captured spies received considerable media coverage. Despite this, the Department of War, which was dominated by the United States Army, advised President Franklin D. Roosevelt on 11 December that the threat of missile attack was so low that it did not justify the diversion of resources from other tasks. This assessment was not supported by the U.S. Navy.

In response to the perceived threat, the U.S. Atlantic Fleet prepared a plan to defend the east coast from attacks by aerial raiders and missiles. This plan was originally code-named Operation Bumblebee, and later renamed Operation Teardrop. Completed on 6 January 1945, the plan involved U.S. Navy anti-submarine forces as well as United States Army Air Forces and Army units, which were responsible for shooting down attacking aircraft and missiles. The centerpiece of the plan was the formation of two large naval task forces to operate in the mid-Atlantic as a barrier against submarines approaching the east coast. These task forces were formed from several existing escort carrier groups, and used Naval Station Argentia, Newfoundland, as their forward operating base. As well as guarding against missile attacks, these large forces were tasked with countering the new and high-performance Type XXI submarines if they began operating in the central Atlantic. The Atlantic Fleet's commander, Vice Admiral Jonas H. Ingram, gave a press conference on 8 January in which he warned there was a threat of missile attack and announced that a large force had been assembled to counter seaborne missile launchers.

In January 1945, German Minister of Armaments and War Production Albert Speer made a propaganda broadcast in which he claimed that V-1 and V-2s "would fall on New York by February 1, 1945", increasing the U.S. Government's concern over the threat of attack. However, the Germans had no ability to fire missiles from their submarines, as both attempts to develop submarine-launched rockets ended in failure. In June 1942, U-511 was used to trial small and short-ranged artillery rockets which could be fired while submerged. Development of this system ended in early 1943, as it was found to decrease the U-boats' seaworthiness. The German military also began the development of a U-boat-towed launch canister for the V-2 ballistic missile in November 1944. Once complete, these canisters were to be towed to a position off the United States east coast and be used to attack New York. Vulkan Docks in Stettin was contracted to build a prototype in March or April 1945, but little work took place before Germany's final collapse. It is unlikely that the system would have been successful if it had been completed.

Nine Type IX U-boats were dispatched from Norway to patrol off Canada and the United States in March 1945 and attack shipping. The purpose of this deployment was to divert Allied anti-submarine forces away from the coastal waters of the United Kingdom. These waters were the main operational area for German submarines in early 1945, but heavy casualties had forced the German navy to break off operations in late March. On 12 April, U-518, U-546, U-805, U-858, U-880, U-881 and U-1235 were designated "Gruppe Seewolf" ("Group Seawolf") and ordered to attack shipping from New York southwards. The remaining two boats, U-530 and U-548, were directed to Canadian waters.