Harold Williams MSc PhD FRSC (14 March 1934 – 28 September 2010) was one of the premier field geologists in the history of Newfoundland geology and the foremost expert on the Appalachian Mountains of North America. An expert on the evolution and tectonic development of mountain belts, Williams advanced the theory of colliding super-continents in the 1960s and 1970s by helping to transform the notion of continental drift into the theory of plate tectonics.