Rhys Llywelyn Isaac (born 1937 in Cape of Good Hope) is Emeritus Professor of American History at La Trobe University, Australia and Distinguished Visiting Professor of Early American History at the College of William and Mary, Williamsburg, Virginia. In 1983 he won the Pulitzer Prize for History for his book The Transformation of Virginia, 1740-1790. 2005 saw the publication of Isaac's Landon Carter's Uneasy Kingdom: Revolution and Rebellion on a Virginia Plantation, which made use of the exemplary diary of a Virginian landholder and sometimes colonial representative.
