The letter of three hundred (Russian: "Письмо трёхсот") was a 22-page memorandum signed by about 300 scientists in order to highlight the destruction of Soviet science in general and genetics in particular by the pseudoscientist Trofim Lysenko.
It resulted in the resignation of T. D. Lysenko from his position as president of the VASKhNIL, despite support for him from Nikita Khrushchev who had taken command after the death of Joseph Stalin.
The letter highlighted the shame brought to Soviet science by Lysenko and his supporters who travelled and spoke around the world providing what they claimed as food for anti-Soviet propaganda.
The letter resulted in the resignation of Lysenko from the position of president of VASKhNIL in 1956 but through Khrushchev's influence he returned to power in 1958-59.
In February 1965, Lysenko was finally dismissed from the institute of genetics, and later on a commission revealed many of his unethical practices, irreparably damaging his reputation.