Raemer E. Schreiber (1910-1998) was an American physicist.
Schreiber joined the Manhattan Project at Los Alamos in November 1943. He worked on the Water Boiler, an aqueous homogeneous reactor used to test critical mass. In 1945, Schreiber was transferred to the Gadget Division and was a member of the pit assembly team for the Trinity Test, watching the explosion from base camp. He flew to Tinian Island with two plutonium hemisphered and helped assemble the Fat Man bomb used on Nagasaki.
After the war, Schreiber continued working at Los Alamos National Laboratory as group leader of the Weapons Division. He led the pit teams on Bikini Atoll in the summer of 1946. Schreiber became an advocate for the remote handling of dangerous substances after he witnessed the death of Louis Slotin, who was exposed to a fatal amount of radiation during a criticality accident at Los Alamos.
Schreiber became head of the Weapons Division in 1951 and began working on the development of the hydrogen bomb. He helped test the first thermonuclear device at Eniwetok Atoll. In 1955 Schreiber became head of the Nuclear Rocket Propulsion Division, working on nuclear rockets for space exploration.