Thomas Richard Holtz, Jr., Ph.D. (born 1965 in Los Angeles) is an American vertebrate palaeontologist and senior lecturer at the University of Maryland's Department of Geology. He has published extensively on the phylogeny, morphology, ecomorphology, and locomotion of terrestrial predators, especially on tyrannosaurids and other theropod dinosaurs. He wrote the book and is the author or co-author of the chapters "Saurischia", "Basal Tetanurae", and "Tyrannosauroidea" in the second edition of The Dinosauria. He has also been consulted as a scientific advisor for the Walking With Dinosaurs BBC series.