Michael Dennis Nahan (born 2 July 1950) is an American-born Australian politician, serving as Western Australian Liberal leader and Leader of the Opposition from the 2017 state election until his resignation in June 2019.
He has been Liberal member of the Western Australian Legislative Assembly seat of Riverton since 2008.
He served as the Treasurer of Western Australia from March 2014 until March 2017, during which time he supervised the loss of the state's triple-A credit rating.