Allen's hummingbird was formally described by the French naturalist René Lesson in 1829 and given the binomial name Ornismya sasin. The specific epithet is a Wakashan or Nootka Native American name for a hummingbird. The type locality is San Francisco. Allen's hummingbird is now placed in the genus Selasphorus that was introduced by William Swainson in 1832. The title page bears the year 1831 but the volume did not appear until 1832. The common name commemorates Charles Andrew Allen, an American collector and taxidermist who identified the bird in 1879 in Nicasio, California.
