Project Sherwood was the codename for a United States program in controlled nuclear fusion during the period it was classified. After 1958, when fusion research was declassified around the world, the project was reorganized as a separate division within the United States Atomic Energy Commission (AEC) and lost its codename.
Sherwood developed out of a number of ad hoc efforts dating back to about 1951. Primary among these was the stellarator program at Princeton University, itself code-named Project Matterhorn. Since then the weapons labs had clamored to join the club, Los Alamos with its z-pinch efforts, Livermores magnetic mirror program, and later, Oak Ridges fuel injector efforts. By 1953 the combined budgets were increasing into the million dollar range, demanding some sort of oversight at the AEC level.
The name "Sherwood" was suggested by Paul McDaniel, Deputy Director of the AEC. He noted that funding for the wartime Hood Building was being dropped and moved to the new program, so they were "robbing Hood to pay Friar Tuck", a reference to the British physicist and fusion researcher James L. Tuck. The connection to Robin Hood and Friar Tuck gave the project its name.
Lewis Strauss strongly supported keeping the program secret until pressure from the United Kingdom led to a declassification effort at the 2nd Atoms for Peace meeting in the fall of 1958. After this time a number of purely civilian organizations also formed to organize meetings on the topic, with the American Physical Society organizing meetings under their Division of Plasma Physics. These meetings have been carried on to this day and were renamed International Sherwood Fusion Theory Conference. The original Project Sherwood became simply the Controlled Thermonuclear Research program within the AEC and its follow-on organizations.