Wisconsin Highway 57 (often called Highway 57, STH-57 or WIS 57) is a 191.82-mile-long (308.70 km) state highway in Wisconsin, United States. It runs from its southern terminus at WIS 59 in Milwaukee to its northern terminus at WIS 42 in Sister Bay. Much of WIS 57 parallels Interstate 43 (I-43) and WIS 42, particularly from Saukville to its northern terminus in Sister Bay. The highway runs concurrently with I-43 for 12 miles (19 km) in Ozaukee County. Like most Wisconsin state highways, WIS 57 is maintained by the Wisconsin Department of Transportation (WisDOT).

WIS 57 serves as a major highway in eastern Wisconsin, and it was originally designed to connect the major cities of Milwaukee and Green Bay as well as several other large cities along its corridor. The state of Wisconsin proposed that the WIS 57 route become an Interstate Highway corridor when the Interstate Highway System was planned in the 1950s; the state's plan was rejected in favor of the current routing of I-43, though it remains a popular and marked alternate route for both I-43 and I-41 to the west. WIS 57 is also a major route to the tourist area of Door County; it is one of only two state highways to serve the county with WIS 42.

WIS 57 begins at WIS 59 (National Avenue) in Milwaukee and continues north as Layton Boulevard until just south of I-94 where the road name becomes 27th Street. Continuing north of I-94 for eight blocks, WIS 57 turns east onto US 18 (Highland Avenue) before turning north eight blocks later while US 18 parts south towards Marquette University. For almost a mile, WIS 57 heads towards WIS 145 only to turn a block north towards WIS 190. Moving eastward again on WIS 190, WIS 57 heads for I-43 before turning northwestwardly onto Green Bay Road. In Brown Deer, WIS 57 meets WIS 100 (formerly as a diamond interchange until reconstruction in 2023), and continues north for Ozaukee County.

In Ozaukee County, WIS 57 turns right onto WIS 167 and approaching I-43 while WIS 167 ends at the interchange. For the next 12 miles, WIS 57 will run concurrent with I-43 before departing the freeway northwest of Port Washington, where the road runs on a nearly straight line for 31.5 miles (50.7 km). This is also one of two concurrencies with WIS 32, the other being along the stretch between Millhome and De Pere. WIS 57 then transitions into an expressway, passing by Fredonia, Random Lake, Adell, and Waldo in Ozaukee and Sheboygan Counties. WIS 57 transitions back into a rural two lane highway north of WIS 23 in Plymouth and continues in its form until where its meet up with WIS 32 just north of the Sheboygan–Manitowoc county line.

Entering Manitowoc County, WIS 32/57 expands back into an expressway all the way until Kiel. WIS 67 intersects with WIS 32/57 and provides access to Kettle Moraine and Manitowoc (via U.S. 151) at WIS 67's northern terminus. Zigzagging through Kiel, WIS 32 and 57 enter Calumet County and passes by New Holstein before entering the county seat, Chilton. While in Chilton, the two routes connect with U.S. 151 which the latter provides access towards Manitowoc and Sturgeon Bay along the scenic Schooner Coast. Before exiting Calumet County, WIS 32/57 would intersect with WIS 114 and U.S. 10 in Hilbert and Forest Junction respectively. U.S. 10 connects WIS 32/57 with Appleton and Manitowoc, while WIS 114 leads drivers towards Lake Winnebago.

WIS 96 is the first state highway to be crossed by WIS 32/57 in Brown County, connecting to Appleton and Wrightstown to the west while hooking to I-43 in Denmark to the east. WIS 32/57 enters De Pere from the south and crosses over an incomplete interchange with County Highway PP and regaining two lanes in each direction.

Entering the downtown district, WIS 32 leaves WIS 57 for Pulaski and eventually at the Michigan state line in Land O' Lakes with U.S. 45 167 miles north-northwest. WIS 57 then straddles closer towards the Fox River and passes under WIS 172 in Allouez before entering Green Bay as Monroe Avenue. While in Green Bay, WIS 57 is joined by WIS 54 and briefly by WIS 29. Getting closer into the core, WIS 29/54/57 intersect with U.S. 141 while WIS 29 heads east along with U.S. 141 for I-43. After crossing the East River, WIS 54/57 turns eastward for I-43 and becomes a freeway after crossing under the latter while carrying the Lake Michigan Circle Tour. From I-43 to Dyckesville, WIS 57 carries the designation as Sturgeon Bay Road and sometimes referred to as the Sturgeon Bay Freeway. Including the interchange with I-43, WIS 54 departs from WIS 57 at the fourth interchange and heads east for Algoma and Luxemburg. WIS 57 from I-43 to WIS 54 has a speed limit of 70 mph (110 km/h) but then slows down to 65 mph (105 km/h). Continuing north-northeast on Sturgeon Bay Road, WIS 57 intersects several county highways and crosses under CTH-S/DK in Dyckesville before entering Kewaunee County. Like in Manitowoc County, WIS 57 leaves Kewaunee County shortly and enters Door County.

While heading towards Sturgeon Bay, WIS 57 intersects with CTH-C. It continues to WIS 42, which connects Sturgeon Bay with Manitowoc. Picking up WIS 42, the two routes then as they enter the city limits of Sturgeon Bay. WIS 42/WIS 57 intersects with CTH-C and CTH-S before crossing over the business routes at an incomplete interchange. The two highway then crosses over the Sturgeon Bay via the Bay View Bridge before intersecting with Michigan Street at a recently constructed roundabout. Bus. WIS 42/Bus. WIS 57 ends at the parent route at another recently constructed roundabout, and the road narrows back down to one primary lane in each direction for the last time. While WIS 42 heads north for Egg Harbor, Fish Creek and Ephraim, WIS 57 turns east for Jacksonport and Baileys Harbor. Before entering Jacksonport, WIS 57 passes through the twin unincorporated communities of Institute and Valmy. WIS 57 then comes close along the Lake Michigan shoreline before entering Baileys Harbor and returning inland for Sister Bay where it ends at WIS 42.