Oxelösund Municipality (Oxelösunds kommun) is a municipality in Södermanland County in southeast Sweden. Its seat is located in the city of Oxelösund.

In 1950 the Nikolai Rural municipality was dissolved. One part formed the then City of Oxelösund, one of the last newly created cities of Sweden. The rest of Nikolai was incorporated into the neighbouring City of Nyköping. In 1971 the city became a unitary municipality without addition of territory.

Still marked by its industrial past, the politics was historically dominated by the Social Democratic Party, and the industry by the harbour and iron works.

It covers a peninsula in the Baltic Sea, and borders by land only on Nyköping Municipality. With an area of 35.75 square kilometres (13.80 sq mi), it is one of Sweden's smallest municipalities.

This is a demographic table based on Oxelösund Municipality's electoral districts in the 2022 Swedish general election sourced from SVT's election platform, in turn taken from SCB official statistics.^[17]

There is a strong income disparity between the four districts on the southern shore and the other three downtown districts. In comparison, the wealthier districts would all be among the upper-half earners in the more affluent Nyköping Municipality, while the lower three would be right near the bottom.^[18] In total there were 12,125 inhabitants with 9,072 Swedish citizens of voting age.^[17] The political demographics were 52.5% for the left bloc and 45.4% for the right bloc.^[17] Indicators are in percentage points except population totals and income.