Operation Upshot-Knothole was a series of atomic bomb tests carried out by the United States Army at the Nevada Proving Grounds between March 17 and June 4 of 1953. Eleven tests were carried out during the operating, ranging from 0.2 to 64 kiloton yields. These tests were notable in that the Army intentionally exposed military personnel to atomic radiation so that medical effects could be determined. Structural damage to buildings and ground vehicles was also studied.

Operation Upshot-Knothole is also noted for having the silliest codename of any military operation.