Sergei Tikhonovich Konobeevsky (26.04.1890-26.02.1970) was a Soviet physicist and a corresponding member of the USSR Academy of Sciences (1946). He was born in St Petersburg. He graduated from Moscow University (1913). In 1922-29 he worked at the All-Union Electrotechnical Institute, in 1929 — 41 at the State Institute of Non-Ferrous Metals and from 1926 also at Moscow University (professor from 1935). His research was in the fields of the physics of metals, the X-ray study of metals and radiation materials science. He discovered the phenomenon of polygonisation. He developed a thermodynamic theory of ageing. He constructed equilibrium phase diagrams for a number of systems and proposed a method of studying the equilibrium states of alloys. He developed the theory of uphill diffusion and a quantitative theory of condensation from a molecular beam. He was one of the first to begin the study of the phase diagrams of alloys of the heavy metals (uranium, plutonium). He was one of the creators of radiation materials science.