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 median income of $88,985 placed it as the only county in Wisconsin on the list of the 100 highest-income counties in the U.S. by median income as of 2020. Its county seat and largest city is Waukesha.

Interstate 94 (I-94) runs east–west through the western, central, and southeastern portions of the US state of Wisconsin. A total of 348.23 miles (560.42 km) of I-94 lie in the state.