Harry "Hap" Younger McSween Jr. is Chancellor's Professor Emeritus of Planetary Geoscience at the University of Tennessee at Knoxville.

He has published papers and popular books about meteorites and planetary exploration, and textbooks on geochemistry and cosmochemistry.

The title of his thesis was "Petrological and geochemical studies in the Coronaca area, Greenwood County, South Carolina".

He has also served on numerous advisory committees for NASA and the National Research Council.

In 2013, he was named the Southeastern Conference (SEC) Universities Professor of the Year.