Katrineholm Municipality (Katrineholms kommun) is a municipality in Södermanland County in southeast Sweden. Its seat is located in the city of Katrineholm.
The present municipality was created in 1971, when the City of Katrineholm (instituted in 1917) was amalgamated with surrounding rural municipalities.
The thirty-first Swedish Prime Minister Göran Persson, while originally from the neighboring municipality of Vingåker, was once the municipal chairman (mayor) of Katrineholm.
Coordinates: 59°00′N 16°12′E / 59.000°N 16.200°E