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 controlled 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:
| Administrative county 1889–1974 |
Local government districts 1974–1996 |
|---|---|
| Cardiganshire | Ceredigion |
| Carmarthenshire | Carmarthen, Dinefwr, Llanelli |
| Pembrokeshire | Preseli, South Pembroke |
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.
The county town and administrative headquarters of Dyfed was Carmarthen whilst the largest settlement was Llanelli. Other significant centres of population included Haverfordwest, Milford Haven and Aberystwyth.
On 1 April 1996, under the Local Government (Wales) Act 1994, Dyfed was broken up and the resultant councils were based on the ancient counties, now restored for administrative purposes: Cardiganshire, the council of which renamed itself Ceredigion, the old Welsh name for the district the following day; Carmarthenshire; and Pembrokeshire. The name Dyfed was retained for such purely ceremonial purposes as the Lord Lieutenancy.