Alan Kooi Simpson (born September 2, 1931) is an American politician and member of the Republican Party, who represented Wyoming in the United States Senate (1979–1997). 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.

Born in Denver, Colorado, Simpson graduated from the University of Wyoming's law school (1958). Simpson served in the Wyoming House of Representatives (1965–1977) and won election to the United States Senate (1978). His father, Milward Simpson, had served in the same seat (1962–1967). Simpson served as the Senate Republican Whip (1985–1995). After serving three terms in the Senate, Simpson declined to seek re-election in 1996.

Since leaving office, Simpson has practiced law and taught at different universities. He also served on the Continuity of Government Commission, the American Battle Monuments Commission, and the Iraq Study Group. In 2010, President Barack Obama appointed him to co-chair the National Commission on Fiscal Responsibility and Reform, which made several recommendations on ways to reduce the national debt. He has been a vocal proponent of amending the U.S. Constitution to overturn Citizens United v. FEC (2010) and allow Congress to set reasonable limits on campaign spending in U.S. elections.