The Celtic cross is a form of Christian cross featuring a nimbus or ring.
The nimbus or ringed shape was appended to the Christian cross and other symbols relatively early, being widespread in the Roman Empire by the late 4th century. In these contexts, it is apparently derived from the earlier Roman garland of victory, worn around the head by victors. The Celtic cross may be a variant of this that emerged in Ireland and Britain in the Early Middle Ages.
Popular legend in Ireland says that the Christian cross was introduced by Saint Patrick or possibly Saint Declan, though there are no examples from this early period. It has often been claimed that Patrick combined the symbol of Christianity with the sun cross to give pagan followers an idea of the importance of the cross. By linking it with the idea of the life-giving properties of the sun, these two ideas were linked to appeal to pagans. Other interpretations claim that placing the cross on top of the circle represents Christ's supremacy over the pagan sun.
The Celtic cross later became a common object in art, architecture, and merchandise during the Celtic Revival. It have since remained popular symbols of Ireland and Celtic identity. The Celtic cross has also been used by some nationalist groups stating a relationship with Celts.
The Celtic cross has also been used by some more general White nationalist groups, possibly due to it being interpreted as a sun cross (a similar but not identical symbol), although another possibility is that some of those using the sun cross may have been wrongly misinterpreted as using the Celtic cross.