Jim Matheos 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, as well as making other appearances with many different bands and artists.

Fates Warning is an American progressive metal band, formed in Hartford, Connecticut, in 1982 by vocalist John Arch, guitarists Jim Matheos and Victor Arduini, bassist Joe DiBiase, and drummer Steve Zimmerman. There have been numerous lineup changes over the course of their 42-year career, and Matheos is the only constant member. As of 2020, the band consists of Matheos, vocalist Ray Alder, bassist Joey Vera, drummer Bobby Jarzombek and guitarist Michael Abdow. Fates Warning also had a revolving cast of drummers and guitarists by the time Jarzombek and Abdow joined the band in 2007 and 2020 respectively.