A Celtic cross combines the cross with a ring surrounding the intersection. It is the characteristic symbol of Celtic Christianity, though it may have older, pre-Christian origins.
In Celtic regions of Britain and Ireland many free-standing upright crosses (see 'High cross') were erected, beginning at least as early as the 8th Century. Some of these 'Celtic' crosses bear inscriptions in runes. There are surviving free-standing crosses in Cornwall and Wales, in the island of Iona and in the Hebrides, as well as the many in Ireland. One candidate for the oldest survivor outside Ireland is the standing cross at Bewcastle, Cumberland, one of a small isolated group of crosses in that area. The most famous standing crosses are the Cross of Kells, County Meath, and the crosses at Monasterboyce, County Louth.
The Neolithic symbol combining circle and cross is the simplest conceivable representation of the union of opposed polarities in the western world. Crossed circles scratched on stones have been recovered from Paleolithic caves sites in the Pyrenees. At the most famous megalithic site in Scotland, Callanish, crossing avenues of standing stones extend from a circle. Scratched into stone or painted on pottery, as on Samarra ware, the crossed-circle symbol appears from the Pyrinees in Old Europe, throughout Anatolia, Mesopotamia and the Iranian plateau to the cities of Mohenjo-daro and Harappa in the Indus River valley. It may be compared to the yin-yang symbol of the eastern world.
In pagan Europe, the crossed circle became the mark of the Norse god Odin. Though other explanations of the Christian combination of circle and cross have been made, it should be noted that the "Celtic" cross is rare outside the former extent of Odin's cult.
It should be noted that the Old English word for 'cross' is 'rood.' The word 'cross' in English derives only indirectly from Latin 'crux, crucis', passing through the intermediary of Old Norse 'krosse' (modern 'kors'). Linguistically it is striking that the pagan Norse raiders ('Vikings') should have impressed their word for 'cross' on the christianized Anglo-Saxons.
The cultural associations of the Celtic cross, with connotations of christianity, 'westernness', and the celtic cultural minority within gallic France, perceived as embattled, (cf Breton nationalism) have recently encouraged its co-option in France as an emblem of several far-right groups including the significantly-named Occident.