George Kistiakowsky (1900-1982) was a Ukrainian-American physical chemist.
He joined the Manhattan Project in late January 1944, leaving his role as chief of the National Defense Research Committee’s Explosives Division. He replaced Seth Neddermeyer as head of X (Explosives) Division and by spring 1945 had over 600 people working on solving the complicated problem of igniting the plutonium core in the atomic bomb. Under Kistiakowsky’s leadership, the complex explosive lenses that would uniformly compress the plutonium sphere to achieve critical mass were developed.