With ancient origins, Samhain is a Gaelic festival held on 1 November, but which begins at sundown the night before, as Celtic days began at sunset. This tradition of beginning celebrations the prior evening is embedded in British culture, including notable dates such as Christmas Eve. Samhain is one of four Gaelic festivals—along with Imbolc, Beltane, and Lughnasa—which hailed the changing seasons. It strongly influenced Halloween as it was later Christianised into All Hallows Day. It was widely celebrated in Ireland, Scotland, and on the Isle of Man, and similar festivals took place in ancient Wales, Cornwall, and western France.
There are several pieces of evidence suggesting Samhain has prehistoric origins, including Neolithic burial chambers and passage tombs in Ireland that align with sunrise on Samhain, and references to the date in 9th Century Irish literature. Samhain shares similarities with Beltane, in that both were seen as times of liminality where the wall between the world and the Otherworld thinned. People believed this allowed the aos sí, or fairies and spirits, to cross over. Bonfires were integral to this, providing light and heat, but also a means to offer sacrifices to ensure people and livestock survived the Winter.
The duty of these virgins was to keep constantly alive the fires of Bèl, or the Sun, and of Samhain, or the Moon, which customs they borrowed from their Phœnician ancestors.Geoffrey Keating, Foras Feasa ar Éirinn, translated by John O’Mahony
Mealtimes at Samhain involved setting places for dead relatives, as it was believed their spirits would be able to visit. People would dress up to disguise themselves from the spirits and go door to door, performing mummers plays or singing in exchange for food or favours. Bonfires would be lit upon hilltops to offer blessings to the parish but also to light the way of wandering spirits. Fires also offered heat and light like the waning sun which was staved off Winter and could burn up harmful influences. Torches would be made from these fires and carried to homes, then brought room to room sunward to cleanse and protect them. Stones would be placed around fires and then dancing would commence. If any stones were moved, the placer would face their own mortality before the next Samhain. In coastal communities, offerings would be made to the sea for prosperity and blessings. These were often to appease spirits, as though some would be welcoming and friendly, other more malevolent souls were believed to return to this world seeking revenge.
Samhain was appropriated by early Christianity into Hallowtide, with the evening celebrations becoming Halloween and the main day All Hallows Day, later All Saints Day. The following day became All Souls Day, and many traditions of Samhain were absorbed into the evolving rituals of Hallowtide. It has seen some revival through Wicca and Neopaganism, along with general interest through folklore enthusiasts and historians, and has also thrived in popular culture, particularly through horror films.