"O Splendor of God's Glory" (Splendor Paternae gloriae) is one of the earliest Christian hymns, composed by St. Ambrose of Milan in the 4th century. It represents the emergence of Latin hymnody in the Western church and is noted for its theological depth and poetic structure. The hymn has been sung for centuries in various plainchant traditions, particularly the Sarum rite, and continues to be used in liturgical settings today.