Phi Sigma Kappa (ΦΣΚ), colloquially known as Phi Sig or PSK, is a men's social and academic fraternity with approximately 74 active chapters and provisional chapters in North America. Most of its first two dozen chapters were granted to schools in New England, New York, and Pennsylvania; therefore its early development was strongly Eastern in character, eventually operating chapters at six of the eight Ivy League schools as well as more egalitarian state schools. It later expanded to the South and West.

In North America, fraternities and sororities are social organizations at colleges and universities. They are sometimes collectively referred to as Greek life. Generally, membership in a fraternity or sorority is obtained as an undergraduate student but continues thereafter for life. Some accept graduate students as well. Individual fraternities and sororities vary in organization and purpose, but most share five common elements:Secrecy Single-sex membership Selection of new members based on a two-part vetting and probationary process known as rushing and pledging Ownership and occupancy of a residential property where undergraduate members live A set of complex identification symbols that may include Greek letters, armorial achievements, ciphers, badges, grips, hand signs, passwords, flowers, and colors