Mathesar is a character in the 1999 film Galaxy Quest portrayed by Enrico Colantoni. Mathesar is the leader of the Thermians aboard the Protector. Like with all his race, he believes the Galaxy Quest TV show to be real.

Mathesar is later promoted to commander of the Protector by its former commander Peter Quincy Taggart.

His true form is a reddish-orange octopus creature.

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