Gille Críst is the first known Mormaer (in Scotland, a regional or provincial ruler, equivalent to Latin comes, French comte and English earl) of Menteith, but almost certainly not actually the first. He is named in a charter of King Máel Coluim IV, dated to 1164, regarding the restoration of Scone Priory, which had recently been destroyed by fire. He appears again in a charter of King William the Lion, dated 1175x1178, as one of the witnesses to a grant of privileges to the newly established burgh of Glasgow.
Gille Críst had two known sons, Muireadhach Mór and Muireadhach Óg. He also had a daughter, Éua, who married Ailín II, Earl of Lennox.
Gille Críst had died by 1189/1198, when Muireadhach Mór appears as Mormaer for the first time.