Phi Sigma Gamma (ΦΣΓ or PSG) is an American men's osteopathic medical fraternity.

[3] The mission of Phi Sigma Gamma is to facilitate the creation and maintenance of professional, as well as social, relationships between medical students and practicing physicians.

The fraternity was originally formed in the academic year of 1915–1916 with president Bizzell's home in Bryan as a base of operations.

[2][6] In 1919, to protest the United States entering World War I, Phi chapter changed the order of its Greek letters to "GPS," rather than PSG.

In 1941, freshman student Brian Michael Fitz died of alcohol poisoning at the Phi chapter at Texas A&M College of Veterinary Medicine & Biomedical Sciences.