Delta Omicron Sigma (ΔΟΣ) is a national veterans' fraternity based in the United States.
Membership is open to all honorably discharged military veterans, current and discharged reservists, and National Guard or Coast Guard members. The intention is to bring "veteran scholars" together - people who, having completed military service, made the choice to further their education.
Delta Omicron Sigma was founded on August 7th, 2003 at Northern Illinois University in DeKalb, Illinois. Originally, Delta Omicron Sigma was intended as a local fraternity to fill the void left by the demise of other national fraternity offices, but during the summer of 2004 it became a national fraternity due to the addition of another chapter in Denver, Colorado.