Oconomowoc is a city in Waukesha County, Wisconsin, United States. The name was derived from Coo-no-mo-wauk, the Potawatomi term for "waterfall." The population was 18,203 at the 2020 census. The city is partially adjacent to the Town of Oconomowoc and near the village of Oconomowoc Lake, Wisconsin.

Waukesha County is a county in the U.S. state of Wisconsin. As of the 2020 United States Census, the population was 406,978, making it the third-most populous county in Wisconsin. Its county seat and largest city is Waukesha.