Alexei Alexeivich Zavarzin (Zawarzin in German publications, Russian: Алексей Алексеевич Заварзин) (25 March 1886 – 25 July 1945) was a Soviet histologist and biologist.

Zavarzin was born in St. Petersburg where his father Alexei Amplievich and mother Anna Savelyevna (Stepanova) ran a mechanic workshop.

He had to study Latin and separately pass an exam before he was admitted to St. Petersburg University.

He headed the department of histology at the Military Medical Academy and in 1932 he moved to the All-Union Institute of Experimental Medicine where he worked until his death while also serving in other positions.

He introduced evolutionary thinking into medical research and guided numerous students.