John Randolph Thune is an American politician serving as the senior United States senator from South Dakota, a seat he has held since 2005. A member of the Republican Party, he has been elected the Senate majority leader and Senate Republican leader, a post he is to assume in January 2025. Thune is in his fourth Senate term and is the Senate minority whip, a post he has held since 2021, and the dean of South Dakota's congressional delegation. From 1997 to 2003 he served three terms as the U.S. representative for South Dakota's at-large congressional district.