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.

The two later collaborated as Arch/Matheos, releasing full-length albums Sympathetic Resonance in 2011 and Winter Ethereal in 2019.

On February 17, 2014, Matheos released an experimental guitar album called Halo Effect.

A detailed gear diagram of Jim Matheos' 2012 Fates Warning guitar rig is well-documented.