Jim Matheos (November 22, 1962, Westfield, Massachusetts, United States), 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 various bands and artists.
He has also released two solo instrumental albums on Metal Blade Records.
In 2003, Matheos collaborated with original Fates Warning vocalist John Arch on A Twist of Fate, Arch's first professional recording since leaving Fates Warning in 1986. The two later formed a duo simply called Arch/Matheos, which has released one full-length album so far.
Fates Warning's eleventh album is planned to be released in 2013.