Rhys Llywelyn Isaac (20 November 1937 – 6 October 2010) was a South African-born Australian historian of American history. Isaac won the 1983 Pulitzer Prize for History for his book "The Transformation of Virginia, 1740–1790". He is the only Australian historian to win a Pulitzer Prize. In 1963, he moved to Australia, where he taught at the University of Melbourne. He later worked at La Trobe University from 1971 to 1999, where he was Emeritus Professor of American History. In 1975, Isaac was a Distinguished Visiting Professor of Early American History at the College of William & Mary in Williamsburg, Virginia, United States.