Clyde William Tombaugh (February 4, 1906 – January 17, 1997) was an American astronomer. Although he is best known for discovering the dwarf planet Pluto in 1930, the first object to be discovered in what would later be identified as the Kuiper Belt, Tombaugh also discovered many asteroids; he also called for serious scientific research of unidentified flying objects.

Tombaugh was born in Streator, Illinois. After his family moved to Burdett, Kansas, Tombaugh's plans for attending college were frustrated when a hailstorm ruined their crops. Starting in 1926, he built several telescopes with lenses and mirrors he ground himself. He sent drawings of Jupiter and Mars, as well as his telescopes to the Lowell Observatory. These resulted in a job offer. Tombaugh was employed at the Lowell Observatory from 1929 to 1945.

Following his discovery of Pluto, Tombaugh earned bachelor's and master's degrees in astronomy from the University of Kansas in 1936 and 1938. During World War II he taught naval personnel navigation at Northern Arizona University. He worked at White Sands Missile Range in the early 1950s, and taught astronomy at New Mexico State University from 1955 until his retirement in 1973. He died in Las Cruces, New Mexico in 1997, aged 90. He was survived by his widow, Patricia and their children: daughter Annette and son Alden. Tombaugh was the great-uncle of Los Angeles Dodgers pitcher Clayton Kershaw. Tombaugh was an active Unitarian-Universalist.