Government of the Soviet Union
The Lost Cosmonauts or Phantom Cosmonauts are subjects of a conspiracy theory alleging that some Soviet cosmonauts went to outer space, but their existence has never been publicly acknowledged by either the Soviet or Russian space authorities. Proponents of the Lost Cosmonauts theory argue that the Soviet Union attempted to launch human spaceflights before Yuri Gagarin's first spaceflight, and the cosmonauts onboard died in those attempts. Another cosmonaut, Vladimir Ilyushin, has been the subject of allegations to have landed off course and been held by the Chinese government. The Government of the Soviet Union supposedly suppressed this information, to prevent bad publicity during the height of the Cold War.