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).