Among the symbols of Christianity, the earliest were monograms of the name Jesus

Christ. Of the several monograms of Christ, the chi-rho is the most ancient (also known as

the Christogram). It is a monogram derived from the first two Greek letters in the name

of Christ (ΧΡΙСΤΟΣ “Messiah”) — the letters “X” (chi) and “P” (rho). Although its earlier

use has been documented, it is traditionally dated to the celebrated vision of Constantine

the Great who saw a “cross of light” (Eusebius, Vita Constantini, Book I, Chapter

XXVIII). The labarum or military imperial standard designed after his vision, was a long

spear with a transverse bar forming a cross and on top of the whole was fixed a wreath

within which were a monogram —the letter “X” (chi) intersecting “P” (rho) at the centre.

This labarum accompanied Constantine’s victory over Maxentius in 312 CE. The

Christogram symbolizes the universal victory of Christianity or the victory of the Savior

over the domination of sin.

The Christogram appears as a Christian symbol from the third century CE, as evidenced

by inscriptions carved in stone; for example in the Catacomb of Calixtus in Rome. It

became more widespread from the fourth century onwards as an echo of Constantine’s

vision, appearing in every context and possible form throughout the Christian world.