The Christian cross, seen as a representation of the instrument of the crucifixion of Jesus Christ, is the best-known religious symbol of Christianity. It is related to the crucifix (a cross that includes a usually three-dimensional representation of Jesus' body) and to the more general family of cross symbols.

The cross-shaped sign, represented in its simplest form by a crossing of two lines at right angles, greatly antedates, in both East and West, the introduction of Christianity. It goes back to a very remote period of human civilization. It is supposed to have been used not just for its ornamental value, but also with religious significance.

Some have sought to attach to the widespread use of this sign, in particular in its swastika form, a real ethnographic importance. It may have represented the apparatus used in kindling fire, and thus as the symbol of sacred fire or as a symbol of the sun, denoting its daily rotation. It has also been interpreted as the mystic representation of lightning or of the god of the tempest, and even the emblem of the Aryan pantheon and the primitive Aryan civilization.