William Gambel (June 1823 – December 13, 1849) was an American naturalist and collector.
Gambel was born in Philadelphia. In 1838 he travelled with the naturalist Thomas Nuttall on a collecting trip to North Carolina. In March 1841 he set off alone to collect plants for Nuttall. He travelled west, taking a more southerly route to that taken previously by Nuttall and Townsend. From Independence he followed the Santa Fe Trail, and then along the Old Spanish Trail, arriving in California in early November. He spent 1842 collecting along the California coast, and then joined the US Navy as a secretary, which allowed him to visit all the California mission stations. The new birds he collected included Gambel's Quail (Callipepla gambelii), Mountain Chickadee (Parus gambeli) and Nuttall's Woodpecker (Picoides nuttallii).
Gambel arrived back in Philadelphia in August 1845. In 1848 he qualified as a physician. He died of typhoid whilst crossing the Sierra Nevada mountains in midwinter.