Halloween or Hallowe'en is a tradition celebrated on the night of October 31, most notably by children dressing in costumes and going door-to-door collecting sweets, fruit, and other treats. Apart from this trick-or-treating, there are many other traditional Halloween activities. Some of these include costume parties, watching horror films, going to "haunted" houses, and traditional autumn activities such as hayrides, some of these even "haunted". A more complete coverage of Halloween customs can be found at Halloween traditions.

Halloween originated under a different name as a Pagan festival among the Celts of Ireland and Great Britain with Irish, Scots, Welsh and other immigrants transporting versions of the tradition to North America in the nineteenth century. Most other Western countries have embraced Halloween as a part of American pop culture in the late twentieth century.

Halloween is celebrated in most parts of the Western world, most commonly in the United States, Canada, the UK, Ireland, and with increasing popularity in Australia and New Zealand. In recent years, Halloween has also been celebrated in parts of Western Europe, such as Belgium, France and Spain.