Mosalsk (Russian: Моса́льск) is a town and the administrative center of Mosalsky District in Kaluga Oblast, Russia, located 82 kilometers (51 mi) west of Kaluga, the administrative center of the oblast.

[9] Grand Duchy of Lithuania 1407–1493 Grand Duchy of Moscow 1493–1547 Tsardom of Russia 1547–1721 Russian Empire 1721–1917 Russian Republic 1917 Soviet Russia 1917–1922 Soviet Union 1922–1991 Russian Federation 1991–present First attested in 1231 as Masalsk (Масальск), it became the center of one of the Upper Oka Principalities in the 14th century.

[citation needed] After Ivan III annexed the principality to the Grand Duchy of Moscow in 1493, local princes emigrated either to the Grand Duchy of Lithuania (where they became known as Princes Massalski) or to Moscow (where they were known as Princes Koltsov-Mosalsky).

Mosalsk was granted town status within Kaluga Governorate in 1776.

The town was the birthplace of Professor Alexander Ivanovich Chuprov.