clasau) was a native Christian church in early medieval Wales.
[verification needed] The building was run by a community of clergy and headed by an abod.
This resulted in several sites becoming part of the Benedictine or Augustinian orders, or built upon in the following centuries by Norman churches.
A map of clasau that can be recognised from Welsh documentary sources was provided by William Rees in 1951.
[4] Many of these early clasau were granted as endowments to the monasteries, particularly those of the Cistercians, founded by the Normans and the Welsh Princes.