The Celtic Rite was the Christian form of worship and sacraments in ancient England and Ireland, which spread to monasteries in Germany, France, Switzerland and Italy. In Italy it was practiced under the leadership of St. Columbanus (A.D. 550-615).
The Celtic Rite differed from most other Christian practices in the date of Easter, the manner of baptism, and the form of tonsure.
The Celtic Rite had disappeared by the A.D. 1200s in favor of practices established in Rome.