Phi Kappa Sigma (ΦΚΣ), also known as Phi Kap, Skulls, Skullhouse, or PKS, is an international all-male college secret society and social fraternity. Commonly known as “Skulls”, the name is inspired by the skull and crossbones on the fraternity's badge and coat of arms. Members are often recognized by the solid gold membership pin depicting the fraternity’s symbol, a Maltese Cross surrounding a human skull.