Halloween is a secular holiday combining vestiges of traditional harvest festival celebrations with customs more peculiar to the occasion such as costume wearing, trick-or-treating, pranksterism, and decorative imagery based on seasonal change, death, and the supernatural. It takes place on October 31. Though it was regarded up until the last few decades of the 20th century as primarily a children's holiday, in more recent years common activities such as mask wearing, costume parties, themed decorations, and even trick-or-treating have grown popular with adults as well, making Halloween an all-ages celebration in the new millennium.

The name Halloween (originally spelled Hallowe'en) is a contraction of All Hallows Even, meaning the day before All Hallows Day (better known as All Saints Day), a Catholic holiday commemorating Christian saints and martyrs observed since the early Middle Ages on November 1.