The Lost Cosmonauts or Phantom Cosmonauts are subjects of a conspiracy theory, which alleges that Soviet and Russian space authorities have concealed the deaths of some cosmonauts in outer space. Proponents of the Lost Cosmonauts theory argue that the Soviet Union attempted to launch human spaceflights before Yuri Gagarin's first spaceflight (Vostok 1, 1961), and that cosmonauts onboard died in those attempts. Soviet military pilot Vladimir Ilyushin was alleged 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.
The evidence cited to support Lost Cosmonaut theories is generally regarded as inconclusive, and several cases have been confirmed as hoaxes. In the 1980s, American journalist James Oberg researched space-related disasters in the Soviet Union, but found no evidence of these Lost Cosmonauts. Since the fall of the Soviet Union in the early 1990s, much previously restricted information has been made available, including information on Valentin Bondarenko, a would-be cosmonaut, whose death during training on Earth was covered up by the Soviet government. Even with the availability of published Soviet archival material and memoirs of Russian space pioneers, no evidence has emerged to support the Lost Cosmonaut theories. Ilyushin, who died in 2010, also never gave any support to conspiracy theories.
