Nikolai Yevgrafovich Kochin (Russian: Николай Евграфович Кочин; 19 May 1901, St Petersburg – 31 December 1944, Moscow) was a Russian and Soviet mathematician specialising in applied mathematics, and especially fluid and gas mechanics.

He taught mathematics and mechanics at Leningrad State University from 1924 to 1934.

In 1928 Kochin spent a semester in Göttingen, where he helped Gamow to solve the alpha decay problem through quantum tunneling.

Kochin's research was on meteorology, gas dynamics and shock waves in compressible fluids.

Kochin wrote textbooks on hydromechanics and vector analysis: