| Sergei Illarionovich Vasilchikov | |
| Birth Date: | 9 September 1849 |
| Birth Place: | Kiev, Russian Empire |
| Death Place: | Versailles, Yvelines, France |
| Allegiance: | Russian Empire |
| Branch: | Imperial Russian Army |
| Rank: | General of the cavalry |
| Commands: | 2nd Brigade, 2nd Guards Cavalry Division 12th Cavalry Division 1st Cavalry Division 1st Guards Corps (Russian Empire) |
| Battles: | Russo-Turkish War (1877–1878) |
Sergei Illarionovich Vasilchikov (9 September 1849 – 27 August 1926) was an Imperial Russian division commander.He was born in Kiev in modern-day Ukraine. He was the son of Imperial Russian general Illarion Illarionovich Vasilchikov. He fought in the war against the Ottoman Empire. He was promoted to major general in 1891 and lieutenant general in 1899. He was the father of Hilarion Vassilchikov. After the October Revolution, he went into exile.