Wisconsin ( wiss-KON-sin) is a state in the Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin is the 20th-largest state by population and 23rd-largest by area. It has 72 counties and as of the 2020 census had a population of nearly 5.9 million. Its most populous city is Milwaukee; its capital and second-most populous city is Madison. Other urban areas include Green Bay, Kenosha, Racine, Eau Claire, and the Fox Cities.

Wisconsin's geography is diverse, shaped by Ice Age glaciers except in the Driftless Area. The Northern Highland and Western Upland along with a part of the Central Plain occupy the state's western part, with lowlands stretching to Lake Michigan. Wisconsin is third to Ontario and Michigan in the length of its Great Lakes coastline. Its northern portion is home to the Chequamegon-Nicolet National Forest. At the time of European contact, the area was inhabited by Algonquian and Siouan nations, and today it is home to eleven federally recognized tribes. Originally part of the Northwest Territory, it was admitted as a state in 1848. During the 19th and early 20th centuries, many European settlers entered the state, mostly from Germany and Scandinavia. Wisconsin remains a center of German American and Scandinavian American culture, particularly in respect to its cuisine, with foods such as bratwurst and kringle.

Wisconsin is one of the nation's leading dairy producers and is known as "America's Dairyland"; it is particularly famous for its cheese. The state is also famous for its beer, particularly and historically in Milwaukee, most notably as the headquarters of the Miller Brewing Company. Wisconsin has some of the nation's most permissive alcohol laws and is known for its drinking culture. Its economy is dominated by manufacturing, healthcare, information technology, and agriculture—specifically dairy, cranberries, and ginseng. Tourism is also a major contributor to its economy. The gross domestic product in 2020 was $348 billion. Wisconsin is home to one UNESCO World Heritage Site, comprising two of the most significant buildings designed by Wisconsin-born architect Frank Lloyd Wright: his studio at Taliesin near Spring Green and his Jacobs I House in Madison. The Republican Party was founded in Wisconsin in 1854; in modern elections, it is considered a swing state.