Lake Santee is an unincorporated town and census-designated place in Decatur and Franklin counties, Indiana, United States. As of the 2020 census, Lake Santee had a population of 889.
Lake Santee was built up in the 1960s as a housing development centered on a reservoir of the same name.
Lake Santee is located in southeastern Indiana. It is situated northeast of Greensburg and northwest of Batesville.
According to the U.S. Census Bureau, the CDP has a total area of , of which is land and , or 12.60%, is water. The water area consists entirely of Lake Santee, the reservoir.
The portion in Decatur County is in the Decatur County Community Schools school district.
The portion in Franklin County is almost entirely in Batesville Community School Corporation, with a small piece in Franklin County Community School Corporation.