James Dillon (born 29 October 1950) is a Scottish composer who is often regarded as belonging to the New Complexity school. Dillon studied art and design, linguistics, piano, acoustics, Indian rhythm, mathematics and computer music, but is self-taught in composition.

Dillon was born in Glasgow, Scotland. Honours include first prize in the Huddersfield Contemporary Music Festival in 1978, the Kranichsteiner music prize at Darmstadt in 1982, and an unprecedented five Royal Philharmonic Society composition awards, most recently for his chamber piece Tanz/Haus: triptych 2017. The recording of his chamber opera, Philomela, won the Grand Prix de l’Académie du Disque Lyrique 2010. Dillon taught at Darmstadt from 1982 to 1992, and has been a guest lecturer and composer at various institutions around the world. He taught at the University of Minnesota School of Music in Minneapolis, Minnesota, from 2007 to 2014.