Tripp County is a county in the U.S. state of South Dakota. As of the 2020 census, the population was 5,624. Its county seat is Winner. The county was created in 1873, and was organized in 1909. It is named for lawyer, judge, and diplomat Bartlett Tripp.

A county seat is an administrative center, seat of government, or capital city of a county or civil parish. The term is in use in five countries: Canada, China, Hungary, Romania, and the United States. An equivalent term, shire town, is used in the U.S. state of Vermont and in several other English-speaking jurisdictions. County towns usually serve a similar function in Ireland, Jamaica, and the United Kingdom.