Jim Matheos (born November 22, 1962) is an American guitarist and the primary songwriter for the progressive metal band Fates Warning, in which he has been the only consistent member since the group's beginning. Matheos also plays in OSI alongside Kevin Moore (Chroma Key, ex-Dream Theater), as well as making other appearances with many different bands and artists.
In 2003, Matheos collaborated with original Fates Warning vocalist John Arch on 2003's A Twist of Fate, Arch's first professional recording since leaving Fates Warning in 1987. The two later collaborated as Arch/Matheos, releasing full-length albums Sympathetic Resonance in 2011 and Winter Ethereal in 2019.
Fates Warning has released thirteen studio albums since their formation in 1982. Their latest studio album, Long Day Good Night, was released in 2020.
On February 17, 2014, Matheos released an experimental guitar album called Halo Effect. It was released by the independent record label Burning Shed.