| Nikolay Yakovlevich Demyanov | |
| Birth Place: | Tver |
| Death Place: | Moscow |
| Field: | Organic chemistry |
| Alma Mater: | Imperial Moscow University (1886) |
| Education: | Doctor of Science (1899) Academician of the Russian Academy of Sciences |
| Thesis Title: | On the action of nitric anhydride and nitrogenous oxide on hydrocarbons of the ethylene series |
| Doctoral Advisor: | Vladimir Markovnikov |
| Known For: | Demjanov rearrangement |
Nikolay Yakovlevich Demyanov (ru|Никола́й Я́ковлевич Демья́нов;, Tver – March 19, 1938, Moscow), also known as Demjanov and Demjanow, was a Russian organic chemist and a member of the USSR Academy of Sciences (1929). He is internationally known for the Demjanov rearrangement organic reaction and other discoveries.
He was a recipient of the Lenin Prize in 1930.