Flandreau is a city located in South Dakota, United States. It serves as the county seat of Moody County and had a population of 2,372 according to the 2020 census.
The city was named in honor of Charles Eugene Flandrau, who served as a judge in both the territory and state of Minnesota. Flandrau is historically recognized for saving the community of New Ulm, Minnesota, from destruction during a conflict with the Sioux tribe in 1862.