Halloween , or Hallowe’en, is a holiday celebrated on the night of October 31. Halloween activities include trick-or-treating, ghost tours, bonfires, costume parties, visiting "haunted houses" , carving Jack-o'-lanterns , reading scary stories and watching horror movies . Irish immigrants carried versions of the tradition to North America in the nineteenth century.

Other western countries embraced the holiday in the late twentieth century. Halloween is celebrated in several countries of the Western world, most commonly in Ireland (where it originated), the United States, Canada, Puerto Rico, the United Kingdom, New Zealand, and occasionally in parts of Australia.

Halloween has its origins in the ancient Celtic festival known as Samhain. The festival of Samhain is a celebration of the end of the harvest season in Gaelic culture, and is sometimes regarded as the "Celtic New Year". Traditionally, the festival was a time used by the ancient pagans to take stock of supplies and slaughter livestock for winter stores.

The ancient Gaels believed that on October 31 , now known as Halloween, the boundary between the alive and the deceased dissolved, and the dead become dangerous for the living by causing problems such as sickness or damaged crops. The festivals would frequently involve bonfires, where the bones of slaughtered livestock were thrown. Costumes and masks were also worn at the festivals in an attempt to mimic the evil spirits or placate them.