Samhain marked the end of the harvest and the start of winter in early Irish tradition. It is the oldest festival name we have from Ireland, the setting of several of the great stories, and one of the roots of modern Halloween, though less directly than the usual version suggests.
Samhain (usually pronounced "SOW-in") falls on the night of 31 October into 1 November, halfway between the autumn equinox and the winter solstice. In the old Irish year it was one of four quarter-day festivals, alongside Imbolc in early February, Bealtaine in early May and Lúnasa in early August. Where Bealtaine opened summer, Samhain opened the dark half of the year.
In practical terms it was a hinge in the farming calendar. Cattle came in from the summer pastures, stores were counted, animals were chosen for slaughter or for keeping through the winter, and communities gathered. In modern Irish the night is still Oíche Shamhna, and Samhain is also the word for the month of November. The full entry is at Samhain.
Irish tradition says that on Samhain the boundary between this world and the Otherworld grew thin. The Aos Sí, the people of the mounds, were thought to move freely, the dead were believed to walk among the living, and ordinary rules relaxed for a night. That belief is the reason so many of the old stories choose this night for their most dangerous events.
In Cath Maige Tuired, the tale of the Second Battle of Moytura, the Dagda meets the Morrígan at the river Unius at Samhain, and she promises her help against the Fomorians before the battle. It is one of the clearest examples of the festival working as a threshold: an alliance with the Otherworld is made on the one night it can be.
Another Samhain story belongs to Fionn mac Cumhaill. Each year a figure from the Otherworld, Aillen mac Midgna, lulled the court at Tara to sleep with music and burned the hall. Fionn stayed awake and killed him, which is part of how the young Fionn earned his place as leader of the Fianna.
The medieval tale Echtra Nerai, "The Adventures of Nera", is set on Samhain night in the court of Ailill and Medb at Cruachan. Nera is sent out to tie a withe around the foot of a hanged prisoner and is led into the Otherworld, where he sees a vision of the court's destruction. It is a good example of how the festival is used in the early literature as a night when the other world opens.
The creatures most tied to Samhain are known from folklore collected in the 19th and 20th centuries rather than from a single medieval text, so the details vary from place to place.
Samhain customs recorded in Irish folk tradition include bonfires, whose embers were carried home to relight the hearth for winter; dressing up or disguising so that wandering spirits would not recognise you; and games of divination to learn who you would marry or whether you would live to see the next year. Foods such as barmbrack, a fruit loaf with a ring baked into it, and colcannon with small tokens hidden in it were part of those games. Turnips and potatoes, not pumpkins, were carved into lanterns.
Folklore collections also record leaving a place at the table or keeping the fire lit for the dead of the household. Practice differed from county to county, so these are best read as a range of customs and not a single ritual.
The word Halloween comes from "All Hallows' Eve", the evening before the Christian feast of All Saints on 1 November. All Souls' Day, on 2 November, was fixed around the year 1000. By then the Church had a pair of feasts about the dead on exactly the dates when Irish tradition already held that the dead were close.
Irish and Scottish customs carried abroad by emigrants, especially during the 19th century, reshaped the holiday in North America, where the native pumpkin replaced the turnip. That is the real chain of transmission that is well documented: the folk customs recorded around Samhain in Ireland and Scotland, travelling with emigrants, meeting the Church's own calendar along the way.
What we can and can't say. The name Samhain and its role as a major festival are well attested in early medieval texts. What is much harder to establish is the detail of how pre-Christian communities marked it, because most of our written sources were composed by Christian scribes centuries later. Claims about ancient Samhain rituals, including the idea of a "Celtic New Year" with a fixed set of rites, are traditions and inferences, not documented fact, and some historians argue that much of what we call Halloween grew from medieval Christian practice. This page keeps to what the sources and the folklore record support.
Usually "SOW-in", with the first syllable rhyming with "cow". Regional pronunciations in Irish vary, and you will also hear "SAH-win" in English, but "SOW-in" is the one most Irish speakers would recognise.
Traditionally the night of 31 October into 1 November, midway between the autumn equinox and the winter solstice. In Irish, Halloween is still called Oíche Shamhna, "Samhain night", and Samhain is also the Irish word for November.
Later Irish tradition treats it as the start of the dark half of the year, and medieval sources describe it as a major turning point. How the pre-Christian Irish actually marked it is not well documented, so "Celtic New Year" is best read as a tradition rather than a proven ancient fact.
Partly. Many Halloween customs, including disguise, bonfires, divination games and carved lanterns, are recorded in Irish and Scottish folk tradition around Samhain, and Irish emigrants carried them to North America. Scholars disagree about how much is direct pre-Christian survival and how much grew from the medieval Christian feasts of All Saints and All Souls.
It is the name of the festival and of the month of November in Irish. Medieval writers connected it with the end of summer, and that is the usual explanation, though the old etymology is debated.