| Native Name: | Князство Друцкое (Sla) |
| Conventional Long Name: | Principality of Drutsk |
| Common Name: | Drutsk |
| Subdivision: | Appanage principality |
| Nation: | Polotsk Principality |
| Government Type: | Feudal monarchy |
| Title Leader: | Prince |
| Capital: | Drutsk |
| Today: | Belarus |
| Year Start: | 1101 |
| Year End: | 1565 |
| S1: | Grand Duchy of Lithuania |
| Flag S1: | Lithuanian coat of arms Vytis. 16th century.jpg |
The Principality of Drutsk (Belarusian: Княства Друцкае; obsolete spelling: Druck) was a small appanage of the Principality of Polotsk, centred in the city of Drutsk. It was located on a three way stick between Vitebsk, Minsk and Mogilev regions in modern Belarus.
The appanage principality of Drutsk was established after the death of Vseslav, the Prince of Polotsk, in 1101 and the division of the Polatsk territory between Vseslav's sons. Drutsk was given to Rogvolod-Boris. Soon its territory was taken over by another appanage duchy of Polotsk, Principality of Minsk governed by Gleb Vseslavich. In 1116, the Principality of Drutsk was taken over by the Grand Principality of Kiev governed by Volodymyr Monomakh, but by 1150s it was returned to Principality of Minsk. Eventually Drutsk was entirely taken over by the Principality of Minsk in the second half of the 13th century and in early 14th century by another appanage duchy of Polotsk, Principality of Vitebsk.
It is believed that Algirdas, Grand Duke of Lithuania, acquired the Principality by marriage to Maria of Vitebsk. The principality became part of the Grand Duchy of Lithuania where it existed as an autonomous principality until an administrative reform in 1565–1566, when it was included into the Orsha county of Vitebsk Voivodeship.