John Randolph Thune (born January 7, 1961) is an American politician serving as the senior United States senator from South Dakota, a seat he has held since 2005. Thune is in his fourth Senate term and is the Senate minority whip, a post he has held since 2021. A member of the Republican Party, Thune served three terms as the U.S. representative for South Dakota's at-large congressional district from 1997 to 2003.