Burton "Gus" Guster is a fictional character on the USA Network television comedy Psych and the sequel film series of the same name played by American actor Dulé Hill. He functions as the "straight man" for Shawn Spencer's antics, and provides sobering advice, helpful knowledge, steady support, and friendship.

Gus, born sometime in December 1977, has been Shawn Spencer's best friend since childhood. Together they co-own the detective agency "Psych". Gus attended Pomona College. Gus tends to be strait-laced and more cautious. He is the "Watson" sidekick and has a crucial role in the cases the two solve. Gus is often shown to be academically advanced and knowledgeable on various things, particularly math and science; his experience with pharmaceutical sales aids Shawn in his investigations frequently.^[4] Unlike the Watson-style sidekick, Gus is not often stupefied by Shawn's crime-solving capabilities, and he often doubts how Shawn comes to some of his conclusions. While Shawn is the "superman detective", he does not see himself as above Gus.^[5]

Despite both Shawn and Gus coming to rational conclusions from observable evidence, both occasionally indulge in supernatural explanations for crimes.^[6]

Janée Burkhalter characterizes Gus as a lonely Black nerd, or "blerd", and various references to Black culture or Black identity appear in the show, such as his acapella group "Blackapella" and hobby of tap dancing. In terms of his "nerd" identity, Gus demonstrates extensive knowledge on a wide variety of subjects and studies, as well as adhering to grammatical rules and showing interest in nerdy media. Burkhalter acknowledges that Gus differs from various nerd tropes or stereotypes in that he is often romantically involved and does not always act or dress as a nerd.^[4]

Thornton notes that Gus is also typically the only major Black character for most episodes. The episodes that do, however, feature major Black characters often focus on Gus's friends or family. Thornton also notes that, despite being the sidekick, it is a role that Gus is sometimes reluctant to fulfill, which is a comedic aspect of the show.^[7]