Mosalsky District (Russian: Мосальский райо́н) is an administrative[1] and municipal[4] district (raion), one of the twenty-four in Kaluga Oblast, Russia.

It is located in the west of the oblast.

The area of the district is 1,320 square kilometers (510 sq mi).

[2] Its administrative center is the town of Mosalsk.

[8] The population of Mosalsk accounts for 46.4% of the district's total population.