Lake Wisconsin is a census-designated place (CDP) in Columbia and Sauk counties, in the towns of Lodi and Merrimac, in Wisconsin, United States.

[4] The Columbia County portion of the Lake Wisconsin is part of the Madison Metropolitan Statistical Area, while the Sauk County portion is part of the Baraboo Micropolitan Statistical Area.

As of the census[3] of 2000, there were 3,493 people, 1,419 households, and 1,082 families living in the CDP.

There were 1,419 households, out of which 30.3% had children under the age of 18 living with them, 70.1% were married couples living together, 3.7% had a female householder with no husband present, and 23.7% were non-families.

18.5% of all households were made up of individuals, and 6.4% had someone living alone who was 65 years of age or older.