James Walter "Jim" Christy (born September 15, 1938) is an American astronomer known for discovering Charon, the largest moon of the dwarf planet Pluto.

[1] On June 22, 1978 while working at the United States Naval Observatory, he discovered that Pluto had a moon, which he named Charon shortly afterwards.

His earlier work at the Naval Observatory had included photographing double stars, so it occurred to him that this bulge might be a companion of Pluto.

[4] The photographic evidence was considered convincing but not conclusive (it remained possible that the bulge was due to Pluto having an unexpectedly irregular shape).

[7] On July 14, 2015, he and Clyde Tombaugh's children were guests at the Johns Hopkins Applied Physics Laboratory when the New Horizons spacecraft successfully performed the first flyby of the Pluto-Charon system.