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The Chi Rho (/ˈkaɪ ˈroʊ/; also known as chrismon) is one of the earliest forms of christogram, formed by superimposing the first two (capital) letters—chi and rho (ΧΡ)—of the Greek word ΧΡΙΣΤΟΣ "Christ" in such a way that the vertical stroke of the rho intersects the center of the chi.

The Chi-Rho symbol was used by the Roman emperor Constantine I (r. 306–337) as part of a military standard (vexillum). Constantine's standard was known as the Labarum. Early symbols similar to the Chi Rho were the Staurogram () and the IX monogram ().

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