Yankton is a city in and the county seat of Yankton County, South Dakota, United States.
Yankton had a population of 14,454 at the 2010 census and it is the principal city of the Yankton Micropolitan Statistical Area, which includes the entirety of Yankton County and which had an estimated population of 22,662 as of July 1, 2017. Yankton was the first capital of Dakota Territory. It is named for the Yankton tribe of Western Dakota people; Yankton is derived from the Dakota word I-hank-ton-wan.
Yankton is located on the Missouri River just downstream of the Gavins Point Dam and Lewis and Clark Lake, and just upstream of the confluence with the James River. The United States National Park Service's headquarters for the Missouri National Recreational River are located in the city. The Human Services Center was established as a psychiatric hospital in 1882 and is on the National Register of Historic Places.
Yankton is commonly referred to as the "River City", due to its proximity to the Missouri River and the importance the river played in the city's settlement and development.