Sisseton is a city in Roberts County, South Dakota, United States. The population was 2,479 at the 2020 census. It is the county seat of Roberts County. Sisseton is home to several tourist attractions, including the Nicollet Tower, and is near the "Song to the Great Spirit" building on the Sisseton Wahpeton College campus. The city is named for the Sisseton division of the Sioux people. It also serves as an important part of the Lake Traverse Indian Reservation.