The Wisconsin State Trunk Highway System is the state highway system of the U.S. state of Wisconsin, including Wisconsin's segments of the Interstate Highway System and the United States Numbered Highway System, in addition to its other state trunk highways. These separate types of highways are respectively designated with an I-, US, or STH- (or WIS) prefix. The system also includes minor roads designated as Scenic Byways, four routes intended to promote tourism to scenic and historic areas of the state; and as Rustic Roads, lightly traveled and often unpaved local roads which the state has deemed worthy of preservation and protection. The state highway system, altogether totaling 11,753 miles (18,915 km) across all of Wisconsin's 72 counties, is maintained by the Wisconsin Department of Transportation (WisDOT).

The state of Wisconsin is served by eight Interstate Highways, consisting of five primary routes and three auxiliary routes. The first part of this system was constructed in 1956, and its most recent expansion took place in 2015, with the addition of I-41 to the system. Wisconsin's longest Interstate Highway is I-94, at 348 miles (560 km), and its shortest is I-535, which extends only 1.2 miles (1.9 km) into the state.

There are also fourteen United States Numbered Highways in the state of Wisconsin, which were designated beginning in 1926 and ending in the mid-1930s. The routes of the U.S. Highway System in Wisconsin have remained essentially unchanged since U.S. Highway 16 became a state highway in 1978. There are also several business routes, usually maintained by local governments.

The state of Wisconsin maintains 153 state trunk highways, ranging from two-lane rural roads to limited-access freeways. These highways are paid for by the state's Transportation Fund, which is considered unique among state highway funds because it is kept entirely separate from the general fund, therefore, revenues received from transportation services are required to be used on transportation. The majority of state highway funding comes from gas taxes and vehicle registration fees.

WisDOT also develops and maintains some minor routes, under the designations of Scenic Byways and Rustic Roads. Scenic Byways are minor roads, typically two-lanes, that travel through areas of "scenic and historic interest." Rustic Roads are lightly traveled local roads, sometimes paved and sometimes dirt or gravel, whose rustic characteristics are intentionally maintained and preserved by WisDOT.

All 72 counties in Wisconsin maintain their own system of county highways, which are usually small, have low levels of traffic, and terminate at the limits of cities and towns. Each highway is designated with a label of between one and three letters, and are usually named sequentially, starting with Highway A and continuing to Z, then using double letters from AA to ZZ, and using triple letters if necessary, although this is not a requirement and there are plenty of exceptions.

The various cities, towns, and villages of the state each maintain their own roads beyond this, servicing individual homes and businesses and connecting them to the other systems, although these are not typically referred to as highways.

There are also several types and systems of roads in Wisconsin that are not part of any state or local highway system, and are not specifically constructed or maintained by the state Department of Transportation or by any local agency.