Lake Winnebago (, , ) is a shallow freshwater lake in the north central United States, located in east central Wisconsin. At , it is the largest lake entirely within the state, covering an area of about by with of shoreline, an average depth of , and a maximum depth of . It has many shallow reefs along the west shore and a drop-off type shoreline on the east. Ice blocked water from entering Lake Michigan at Green Bay, and the glacial lake ponded against ice since it had no outlet.
The Niagara Escarpment is a few miles east of Lake Winnebago. The softer Ordovician rocks that underlie the lake have eroded away, and the stronger Silurian rocks stand as a ridge that formed the lake basin.
In 1634, the French encountered the Ho-Chunk on the shores of Green Bay, inhabiting the area stretching to Lake Winnebago. Although "Ho-Chunk" is the people's own name for themselves, their Algonquian neighbors called them "Winnebago", which means "[people of the] stinking water." This term was used by the Algonquians because Lake Winnebago had a strong fish odor in the summer.
The steamer B. F. Carter made a trip from the east shore to the west shore at Oshkosh every two weeks in the 1880s during the summer season.
Lake Winnebago is known for having occasional ice shoves on very windy days in March as the winter ice breaks up. Residents have described that it "sounds like a freight train." Buildings directly on the shoreline have been wrecked by the shoves, which are up to high. Lock reconstruction is underway and is being supervised by the Fox River Navigation Authority.
Recreation
Many annual events take place on the Winnebago Pool, including shoreline concerts, fishing tournaments, power boat events, pleasure boating rallies, windsurfing, sail runs and ice racing.
Boating
Along with the upper lakes of Big Lake Butte des Morts, Winneconne, Poygan, the Wolf River and the upper and lower Fox River, it is a popular pleasure boating area. A 1989 survey of boating intensity by the Wisconsin Department of Natural Resources ranked the Winnebago Pool as the state's busiest inland waterway, surpassing the Mississippi River.
Parks
[[File:LakeWinnebagoNorthHighCliffStateParkObservationTower.jpg|thumb|Looking west at the north end of Lake Winnebago from High Cliff State
Park]]
High Cliff State Park on the lake's northeast shore offers camping, hiking trails, views of the lake, a marina, beach, an observation tower, and picnic areas. Camping is available at Calumet County Park and Columbia County Park in Fond du Lac County. Effigy mounds overlook the lake at High Cliff and Calumet County Park.
Lakeside Park in Fond du Lac is a municipal park on the southern shore of Lake Winnebago with picnic areas, shelters/gazebos, a playground, a deer park, baseball diamonds, a marina, and boat launch ramps. Train rides, an old fashioned carousel, bumper boats, aqua bikes, and canoes are available for rides. A petting zoo is open Memorial Day weekend through Labor Day. The Fond du Lac River enters Lake Winnebago on the eastern border of the park.
Menominee Park in Oshkosh features trails, fishing piers, boat launches, a zoo, a small amusement park, and softball, tennis and basketball facilities. It is the former site of the city's Sawdust Days Festival in July.
Fishing
Lake Winnebago is one of the more heavily fished lakes in the state. The Wisconsin Department of Natural Resources regulates the number of fish taken each year.
Other seasons
Late spring (between May 5 and June 30) is dominated by walleye and sauger fishing.