| Jānis Lācis | |
| Birth Date: | February 20, 1897 |
| Birth Place: | Jaunpiebalga Municipality, Kreis Wenden, Governorate of Livonia, Russian Empire (Now) |
| Death Place: | Khabarovsk, Soviet Union |
| Allegiance: | Russian Empire Soviet Union |
| Branch: | Imperial Russian Army Soviet Red Army |
| Rank: | Komkor |
| Serviceyears: | 1916–1917 (Russian Empire) 1917–1937 (Soviet Union) |
| Battles: | World War I Russian Civil War |
| Commands: | 15th Rifle Division 16th Rifle Corps |
Jānis Lācis (Russian: Ян Я́нович Ла́цис, Yan Yanovich Latsis; February 20, 1897 – March 10, 1937) was a Latvian Riflemen, later Soviet division commander and Komkor (corps commander).
Lacis fought in the 4th Vidzeme Latvian Riflemen Regiment of the Imperial Russian Army in World War I before going over to the Bolsheviks in the subsequent civil war. He was a recipient of the Order of Lenin and the Order of the Red Banner. From 1932 to 1937, he commanded the troops guarding the railways of Siberia and the Far East. He was simultaneously a member of the Central Executive Committee of the Russian Soviet Federative Socialist Republic. He died of an illness in Khabarovsk. He is buried at Novodevichy Cemetery.