Henry Fairfield Osborn (August 8, 1857 — November 6, 1935) was an American paleontologist and geologist.
Osborn was born in Fairfield, Connecticut, and studied at Princeton University. He was professor of comparative anatomy from 1883 to 1890 at Princeton. In 1891 he became professor of biology at Columbia University, becoming professor of zoology in 1896. He was president of the American Museum of Natural History from 1908 to 1935, during which time he accumulated one of the finest fossil collections in the world.
He was mentored by the paleontologist Edward Drinker Cope. He led many fossil-hunting expeditions into the American Southwest, starting with his first to Colorado and Wyoming in 1877. He described and named Tyrannosaurus rex in 1905, and the Velociraptor in 1924. Some of his contributions are less celebrated: Osborn's belief in the now-discredited idea of orthogenesis is one such contribution, his promotion of eugenics, another.
Osborn wrote an influential textbook, The Age of Mammals (1910).