Halloween dates back to the Ancient Celtic festival of Samhain, which is actually the word for Halloween in a few Gaelic languages. The Celts who lived around 2000 years ago in the area that is now Ireland, the United Kingdom, and northern France, threw this Festival on October 31 to celebrate the end of summer and the end of the harvest season. The Celts actually believed that the first day of November marked the beginning of their new year and the onset of winter. To them the days of sunshine had passed and had been replaced by darkness. The cold and gloom of winter was also seen as a time associated with human death.

It was commonly thought by the Celts that on the night before the new year, the boundary between the worlds of the living and the dead became very hazy. Therefore on 31 October, they celebrated Samhain when it was believe that souls of the underworld would return to earth and those that died that year would pass to the next life completely. This would mean the dead and the living would mingle more than at any other time of the year. Samhain was a festival dedicated to the dead and was common for people to tell tales of their ancestors on that night.

Traditionally, Samhain was time to take stock of the herds and grain supplies, and decide which animals would need to be slaughtered in order for the people and livestock to survive the winter. A big bonfire would be lit to unite villages and burn the bones of the slaughtered animals. People gathered to sacrifice animals, fruits, and vegetables. The bonfires were also lit to honor the dead, to aid them on their journey, and to keep them away from the living. It was feared that the dead were powerful on this special evening and as a result may ruin the crops of the harvest if not treated with respect.

Celts thought that the presence of the otherworldly spirits made it easier for the Druids, or Celtic priests, to make predictions about the future. These people were very dependent upon the fruits of the earth and thus the prophecies were very important for them, as they sought comfort for the long, dark winter ahead. Sacred bonfires were also lit by the Druids where the people would gather to burn crops and animals as sacrifices to the Celtic deities. Such practices show how superstitious practices were taken very seriously.

The Festival was the biggest and most significant holiday of the Celtic year, which consisted of four major holidays. During the celebrations the Celts would wear costumes particularly made of animal skins and heads. They also attempted to tell each others' fortunes. When the celebration came to an end, the people would re-light their hearth fires, which they had extinguished earlier that evening, from the sacred bonfire to help protect them during the coming winter.