Dyfed is a preserved county of Wales. It was originally created as an administrative county council on 1 April 1974 under the terms of the Local Government Act 1972, and covered approximately the same geographic extent as the ancient Principality of Deheubarth, although excluding the Gower Peninsula and the area west of the River Tawe. The choice of the name Dyfed was based on the historic name given to the region once settled by the Irish Déisi and today known as Pembrokeshire (the historic Dyfed never included Ceredigion and only briefly included Carmarthenshire). It was formed from the administrative counties (which corresponded to the ancient counties) of Cardiganshire, Carmarthenshire, Pembrokeshire and was divided into the following local government districts:

The Lord Lieutenant of Pembrokeshire became Lord Lieutenant of Dyfed and the Lord Lieutenants of Cardiganshire and Carmarthenshire each became Lieutenants. The Dyfed-Powys police force had been created a number of years earlier.