Preston Ercelle Cloud, Jr. (September 26, 1912 – January 16, 1991) was an eminent American earth scientist, biogeologist, cosmologist, and paleontologist. He served in the United States Navy (in which he was a bantamweight boxing champion), and led several field explorations of the U.S. Geological Survey. In academia, he was member of faculty of Harvard University, University of Minnesota, University of California, Los Angeles, and lastly University of California, Santa Barbara.