State Trunk Highway 31 (often called Highway 31, STH-31 or WIS 31) is a 22.86-mile (36.79 km) state highway in Kenosha and Racine counties in the US state of Wisconsin that runs north–south as a suburban route passing Racine and Kenosha. With the exception of a two-mile (3.2 km) stretch between Four Mile Road and WIS 32 at the north end, WIS 31 is a multi-lane urban highway. An expansion of the remaining two miles (3.2 km) was proposed by the Wisconsin Department of Transportation (WisDOT).