German submarine U-234 was a Type XB U-boat of Nazi Germany's Kriegsmarine during World War II, she was commanded by Kapitänleutnant Johann-Heinrich Fehler.

Her first and only mission into enemy or contested territory consisted of the attempted delivery of uranium oxide and German advanced weapons technology to the Empire of Japan.

Apart from minor work, she had a snorkel added and 12 of her 30 mineshafts were fitted with special cargo containers the same diameter as the shafts and held in place by the mine release mechanisms.

When loading was completed, the submarine's officers estimated that they were carrying 240 tons of cargo plus sufficient diesel fuel and provisions for a six- to nine-month voyage.

[3] The cargo included technical drawings, examples of the newest electric torpedoes, one crated Me 262 jet aircraft, a Henschel Hs 293 glide bomb and what was later listed on the US Unloading Manifest[citation needed] as 550 kg (1,210 lb) of uranium oxide.

The German personnel included General Ulrich Kessler of the Luftwaffe, who was to take over Luftwaffe liaison duties in Tokyo; Kay Nieschling, a Naval Fleet Judge Advocate who was to rid the German diplomatic corps in Japan of the remnants of the Richard Sorge spy ring; Heinz Schlicke, a specialist in radar, infrared, and countermeasures and director of the Naval Test Fields in Kiel (later recruited by the US in Operation Paperclip); and August Bringewalde, who was in charge of Me 262 production at Messerschmitt.

[6] U-234 sailed from Kiel for Kristiansand in Norway on the evening of 25 March 1945, accompanied by escort vessels and three Type XXIII coastal U-boats, arriving in Horten Naval Base two days later.

Then, on 4 May, U-234 received a fragment of a broadcast from British and American radio stations announcing that Admiral Karl Dönitz had become Germany's head of state following the death of Adolf Hitler.

Fehler thought it likely that if they surrendered to Canadian or British forces, they would be imprisoned and it could be years before they were returned to Germany; he believed that the United States would probably just send them home.

During the passage Fehler disposed of his Tunis radar detector, the new Kurier radio communication system, and all Enigma machine-related documents and other classified papers.

Velma Hunt, a retired Penn State University environmental health professor, has suggested U-234 may have put into two ports between her surrender and her arrival at the Portsmouth Navy Yard: once in Newfoundland, to land an American sailor who had been accidentally shot in the buttocks, and again at Casco Bay, Maine.

Those onboard the boat appear to have been told that the contents were dangerous if opened; it is suspected that, if this was not simply a lie meant to keep them from inspecting them more closely, it may have been related to their potential pyrophoricity.

Major John Lansdale, the former head of Manhattan Project security, said in 1995 that the uranium was then directly sent to Clinton Engineer Works in Oak Ridge, Tennessee, where it was enriched as part of the weapons program.