Alan Kooi Simpson is an American politician and member of the Republican Party, who represented Wyoming in the United States Senate from 1979 to 1997. Simpson was the Republican whip in the U.S. Senate from 1985 to 1995, as majority whip from 1985 to 1987 and minority whip from 1987 to 1995. He also served as co-chair of the National Commission on Fiscal Responsibility and Reform with Democratic Party co-chair Erskine Bowles of North Carolina.

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.