Omicron Delta Kappa (ΟΔΚ), also known as The Circle and ODK, is an honor society located in the United States with chapters at more than 300 college campuses. It was founded on December 3, 1914, at Washington and Lee University in Lexington, Virginia, by fifteen student and faculty leaders. The society recognizes achievement in five areas: scholarship; athletics; campus and community service, social or religious activities, and campus government; journalism, speech, and the mass media; and creative and performing arts. Some circles of ΟΔΚ are quasi-secret, in that newly selected members remain undisclosed for some time.

In the United States, an honor society is an organization that recognizes individuals who excel in various domains such as academics, leadership, and other personal achievements, not all of which are based on ranking systems. These societies acknowledge excellence among peers in diverse fields and circumstances. The Order of the Arrow, for example, is the National Honor Society of the Boy Scouts of America. While the term commonly refers to scholastic honor societies, which primarily acknowledge students who excel academically or as leaders among their peers, it also applies to other types of societies.