Chi-Rho

Form

The Greek letters chi (Χ) and rho (Ρ), the first two letters of Christos, laid over each other. Strictly a monogram, not a cross, though the X was also read as a cross.

When it is documented

Constantine’s standard, the labarum (4th century). On Christian sarcophagi and frescoes by about 350.

Context

Lactantius tells of Constantine putting a heavenly sign on his soldiers’ shields, and Eusebius’s later Life of Constantine of a vision and the labarum. The two accounts differ, and the sign Lactantius describes is unclear.

Links in the Atlas

No matching tradition. This form is not the sign of one church, saint or order in the Atlas, and none is assigned to it.

Sources and how they were checked

• Formation, Lactantius and Eusebius accounts, the labarum, use by about 350.

  Wikipedia, “Chi Rho” · checked 2026-10-21 (tertiary reference; Lactantius and Eusebius not inspected)

Not yet known or sourced

• Included because it is constantly shown beside crosses; it has no matching tradition.