Watertown is a city in Codington County, South Dakota, USA. The population was 20,237 at the 2000 census. It is the county seat of Codington County^GR6. Paul S. Fox is the current Mayor. Watertown has one public high school, Watertown Sr. High School, and one private boarding school, Great Plains Lutheran.

Watertown is home to the Redlin Art Center which houses many of the original art works produced by Terry Redlin, one of America's most popular wildlife artists. Watertown also is home to the Bramble Park Zoo, one of only three zoos in South Dakota.