Nikolai Evgrafovoch Kochin (Russian: Николай Евграфович Кочин) (May 19, 1901, St Petersburg – December 31, 1944, Moscow) was a Russian and Soviet mathematician specialising in applied mathematics, and especially fluid and gas mechanics.
Kochin graduated from Petrograd University in 1923. He taught mathematics and mechanics at Leningrad State University from 1924 to 1934.
In 1925 Kochin married Pelageya Polubarinova. They had two daughters.
In 1928 Kochin spent a semester in Göttingen, where he helped Gamow to solve the alpha decay problem through quantum tunneling.
Kochin moved to Moscow 1934. He taught mathematics and mechanics at Moscow State University from 1934 until his death, and was the head of the mechanics section of the Mechanics Institute of the USSR Academy of Sciences from 1939 to 1944. In 1943 Kochin became ill with sarcoma and died in 1944.
Kochin's research was on meteorology, gas dynamics and shock waves in compressible fluids. He gave the solution to the problem of small amplitude waves on the surface of an uncompressed liquid in Towards a Theory of Cauchy-Poisson Waves in 1935. He also worked on the pitch and roll of ships. In aerodynamics he introduced formulae for aerodynamic force and for the distribution of pressure.