William Harrison Frist is an American physician, businessman, conservationist and policymaker who served as a United States Senator from Tennessee from 1995 to 2007. A member of the Republican Party, he also served as Senate Majority Leader from 2003 to 2007. Born in Nashville, Tennessee, Frist studied government and health care policy at Princeton University and earned a Doctor of Medicine degree from Harvard Medical School. He trained as a cardiothoracic transplant surgeon at Massachusetts General Hospital and Stanford University School of Medicine, and later founded the Vanderbilt Transplant Center. In 1994, he defeated incumbent Democratic Senator Jim Sasser.

The positions of majority leader and minority leader are held by two United States senators and people of the party leadership of the United States Senate. They serve as a chief spokespersons for their respective political parties holding the majority and the minority in the United States Senate. They are each elected as majority leader and minority leader by the senators of their party caucuses: the Senate Democratic Caucus and the Senate Republican Conference.