Alexander Aleksandrovich Bogdanov (1873-1928) was a Russian physician, philosopher, science fiction writer, and revolutionary of Belarusian ethnicity. He was a key figure in the early history of the Bolshevik faction of the Russian Social Democratic Labor Party, being one of its cofounders and a rival to Lenin until being expelled in 1909. In the first two decades of the Soviet Union, he was an influential opponent of the government from a Marxist perspective. The polymath Bogdanov received training in medicine and psychiatry. His scientific interests ranged from the universal systems theory to the possibility of human rejuvenation through blood transfusion.