]; December 22, 1869 – September 10, 1931) was a Russian and Soviet mathematician known for contributions to the areas of differential geometry and mathematical analysis.

Egorov held spiritual beliefs to be of great importance, and openly defended the Church against Marxist supporters after the Russian Revolution.

Upon imprisonment, Egorov began a hunger strike until he was taken to the prison hospital, and eventually to the house of fellow mathematician Nikolai Chebotaryov where he died.

[2] Egorov studied potential surfaces and triply orthogonal systems, and made contributions to the broader areas of differential geometry and integral equations.

His work was influenced by that of Jean Gaston Darboux on differential geometry and by Henri Lebesgue in mathematical analysis.