Oleg Igorevich Sumbaev (born 4.02.1930) was a Soviet experimental physicist and a corresponding member of the USSR Academy of Sciences (1979). He was born in Irkutsk. He graduated from the Leningrad Polytechnic Institute (1954). In 1954—57 he worked at the D. I. Mendeleev All-Union Research Institute of Metrology, and in 1957 — 71 at the Leningrad Physico-Technical Institute. From 1972 he was director of the B. P. Konstantinov Leningrad Institute of Nuclear Physics of the USSR Academy of Sciences.
His main work was in the field of atomic and nuclear physics. He detected the effects of chemical and isotopic shift of X-ray lines in heavy elements, and the phenomena of hyperfine broadening and shift of X-ray lines. He studied excited states, charge radii and magnetic moments of nuclei, and the electronic structure of crystal-chemical bonds. He constructed the so-called quasi-mosaic approximation of the theory of diffraction of gamma radiation by elastically deformed single crystals.