Lake Madison is an unincorporated community and census-designated place in Lake County, South Dakota, United States. Its population was 829 as of the 2020 census. The community is located on the shores of Lake Madison.
Lake Madison provides many activities including camping, boating, and fishing. While fishing, you can expect to catch walleye, perch, white bass, crappie, smallmouth bass, and northern pike.
The community is in southeastern Lake County, surrounding Lake Madison. The CDP is southeast of Madison, the county seat. South Dakota Highway 34 forms the northern edge of the CDP. The highway leads west into Madison and east to Interstate 29.
According to the U.S. Census Bureau, the community has an area of ; of its area is land, and is water. Lake Madison drains to the southeast, into Round Lake and then Brant Lake, and is part of the Big Sioux River watershed.
The majority of Lake Madison is in the Madison Central School District 39-2, while portions are in the Chester School District 39-1.