Johnston is a village, parish and community in the former hundred of Roose, Pembrokeshire, Wales, and a parish in the diocese of Diocese of St David's.

The Diocese of St Davids is a diocese of the Church in Wales, a church of the Anglican Communion. The diocese covers the historic extent of Ceredigion, Carmarthenshire and Pembrokeshire, together with a small part of western Glamorgan. The episcopal see is the Cathedral Church of St David in the City of St Davids, Pembrokeshire. The present cathedral, which was begun in 1181, stands on the site of a monastery founded in the 6th century by Saint David.