Dyfed is the name of sub-Roman and Early Medieval kingdom and a late 20th/early 21st century county of Wales.
In the 10th century Hywel Dda united Dyfed and the neighbouring kingdom of Seisyllwg under his rule. The new kingdom became known as Deheubarth and covered an area roughly corresponding to modern Dyfed.
During local government reorganisation in 1974, the newly-created non-metropolitan county covering Cardiganshire, Carmarthenshire and Pembrokeshire was given the name Dyfed.
It was divided into six districts, namely Carmarthen, Ceredigion, Dinefwr, Llanelli, Preseli, South Pembrokeshire.
However, further reorganisation of local government on April 1, 1996, involving the creation of unitary authorities resulted in a return to the status quo ante, with Cardiganshire, Carmarthenshire and Pembrokeshire being restored for administrative purposes.
The name survives as a ceremonial preserved county, and in that of institutions such as Dyfed-Powys Police.
Dyfed | Preserved counties of Wales | Sub-Roman Britain | History of Wales