Samhain was the ancient Celtic festival that marked the end of the harvest season and the beginning of winter.
Traditionally observed around 1 November, Samhain divided the year into the lighter half and the darker half. The festival was especially important in Gaelic culture and was associated with the completion of harvest work, the movement of livestock, and the onset of winter conditions.
Medieval Irish and Scottish sources describe Samhain as a major seasonal gathering. Folklore connected the period with supernatural beings and with a temporary weakening of the boundary between the human world and the otherworld. Fires, feasting, and protective customs became part of its cultural legacy.
Samhain is often called the Celtic origin of Halloween, but Halloween developed through several later Christian and folk traditions as well. Samhain also differs from Lughnasadh, which marked an earlier stage of the grain harvest.