Halloween, or Hallowe'en (a contraction of All Hallows-Evening), also known as All Halloween, All Hallows' Eve, or All Saints' Eve, is a celebration observed in a number of countries on 31 October, the eve of the Western Christian feast of All Hallows' Day.

It begins the three-day observance of All hallow tide, the time in the liturgical year dedicated to remembering the dead, including saints (hallows), martyrs, and all the faithful departed. According to BBC Online, it is "widely believed" that many Halloween traditions originated from the ancient Celtic harvest festival Samhain, and that this Gaelic observance was Christianized by the early Church. Samhain and other such festival had pagan roots. Some, however, support the view that Halloween began independently of Samhain and has solely Christian roots. Halloween activities include trick-or-treating (or the related guising), attending Halloween costume parties, decorating, carving pumpkins into jack-o'-lanterns, lighting bonfires, apple bobbing and divination games, playing pranks, visiting haunted attractions, telling scary stories and watching horror films.