The history of the diocese of St David's is traditionally traced to that saint in the latter half of the 6th century. Records of the history of the diocese before Norman times are very fragmentary, however, consisting of a few chance references in old chronicles, such as 'Annales Cambriae' and 'Brut y Tywysogion' (Rolls Series).
Originally corresponding with the boundaries of Dyfed (Demetia), St David's eventually comprised all the country south of the River Dyfi and west of the English border, with the exception of the greater part of Glamorganshire, in all some 3,500 square miles (9,100 km2). Until 1852 the diocese also included some parishes in Herefordshire.
The office of Bishop of St David's has existed since the founding of the cathedral. The current bishop, the 128th, is the Right Reverend J Wyn Evans, who was elected on 1 September, consecrated on 29 November at Llandaff Cathedral, and enthroned in St Davids Cathedral on 6 December 2008.