Demetrius I of Georgia

Demetrius I held together the realm his father David IV had built, ruling Georgia from 1125 to 1156 with an interruption forced by his own son, and is remembered in Georgia as much for a hymn as for his wars. Born about 1093, he was David's eldest son by his first wife, Rusudan, an Armenian; David's second wife, the Kipchak Gurandukht, was his stepmother. He was a grown man and a proven soldier when his father crowned him co-ruler in 1125 shortly before his death, having led a flanking attack at Didgori in 1121 that the Georgian account credits with breaking the Seljuk line.

His reign was a long defense of exposed frontiers rather than a march of conquest. Shirvan, where his sister Tamar was married to the Shirvanshah Manuchihr III, was settled about 1130 in a compromise that placed its Christian districts under Georgia and left the Muslim remainder to his brother-in-law; Ani, occupied by David in 1124, was restored to the Shaddadids as vassals in negotiations concluded about 1130. In 1139 he raided Ganja after an earthquake had shattered its walls and carried off its iron gates as a trophy to the monastery of Gelati, though the city itself could not be held for long against the Eldiguzids.

His last years were troubled by his sons. Having set aside the elder, David, in favor of the younger, George, Demetrius faced a first coup about 1150 and a successful one in 1154, when David deposed him and sent him to a monastery under the name Damiane. David V died after six months, and Demetrius returned to the throne in 1155 only long enough to crown George III co-ruler before retiring again to the monastery of David Gareja. He died in 1156 and was buried at Gelati beside his father. Besides David V and George III he left a daughter Rusudan, married successively to Seljuk sultans, and another daughter who wed Iziaslav II of Kiev in 1154.

As a monk Demetrius composed the hymn to the Virgin Shen khar venakhi, "Thou Art a Vineyard," still among the most sung pieces of Georgian sacred music. The Georgian church venerates him as Saint Damiane on 23 May.