Theodosius Grygorovych Dobzhansky ForMemRS (Ukrainian:Теодо́сій Григо́рович Добжа́нський; Russian:Феодо́сий Григо́рьевич Добржа́нский; January 25, 1900 – December 18, 1975) was a prominent American geneticist and evolutionary biologist, and a central figure in the field of evolutionary biology for his work in shaping the unifying modern evolutionary synthesis. Dobzhansky was born in Ukraine, then part of the Russian Empire, and became an immigrant to the United States in 1927, aged 27 years old.