Lake Madison, South Dakota

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.

Geography
The community is in southeastern Lake County, surrounding Lake Madison. The CDP is 3 to 10 mi 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 13 mi to Interstate 29.

According to the U.S. Census Bureau, the community has an area of 9.104 mi2; 4.749 mi2 of its area is land, and 4.355 mi2 is water. Lake Madison drains to the southeast, into Round Lake and then Brant Lake, and is part of the Big Sioux River watershed.