Cantref Gwarthaf was the largest of the seven cantrefi of Dyfed

Kingdom of Dyfed

The Kingdom of Dyfed is one of several Welsh petty kingdoms that emerged in 5th-century post-Roman Britain in south-west Wales, based on the former Irish tribal lands of the Déisi from c 350 until it was subsumed into Deheubarth in 920. In Latin, the country of the Déisi was Demetae, eventually to...

. It subsequently became part of Deheubarth in around 950. It consisted of the southeastern part of Dyfed containing most of the basin of the River Tâf

River Tâf

The River Tâf is a river that rises in the Preseli Hills of North Pembrokeshire, West Wales, near the village of Crymych and is around 50 km long....

.

The name means "upper-most zone". Its area was about 631 km². Unlike the other Dyfed cantrefi which were divided into two (or fewer) commotes, Cantref Gwarthaf was divided into eight commotes: Amgoed, Derllys, Efelfre, Elfed, Penrhyn, Peuliniog, Talacharn, and Ystlwys. Its civil headquarters were at Carmarthen

Carmarthen

Carmarthen is a community in, and the county town of, Carmarthenshire, Wales. It is sited on the River Towy north of its mouth at Carmarthen Bay. In 2001, the population was 14,648....

. Its ecclesiastical centre (and perhaps, in the Age of the Saints, the seat of a bishop) was probably also Carmarthen, although the churches at Llanddowror

Llanddowror

Llanddowror is a small, historic, relatively unspoilt village 2 miles from the town of St. Clears in Carmarthenshire in West Wales.- History & Amenities :...

 and Meidrim

Meidrim

Meidrim is a community located in Carmarthenshire, Wales.It has a parish church, a Nonconformist chapel, two pubs, a primary school, a village green or common and a park...

 were also important.

The cantref was made part of the Norman

Normans

The Normans were the people who gave their name to Normandy, a region in northern France. They were descended from Norse Viking conquerors of the territory and the native population of Frankish and Gallo-Roman stock...

 March

Welsh Marches

The Welsh Marches is a term which, in modern usage, denotes an imprecisely defined area along and around the border between England and Wales in the United Kingdom. The precise meaning of the term has varied at different periods...

 in the 12th century. Marcher Boroughs were established at Carmarthen, Llansteffan

Llansteffan

Llansteffan is a village in Carmarthenshire, Wales. Llansteffan is one of three settlements positioned on the Tywi river, other settlements include Ferryside and Carmarthen . Llansteffan Castle, built by the Normans in the 12th century, is located in the village...

, Laugharne and St Clears

St Clears

St Clears is a small town on the River Tâf in Carmarthenshire, Wales. According to the 2001 UK census, it has a population of 2,820 people, most of whom are Welsh-speaking, although there is a marked difference between the southern and northern ends of the town in percentage terms.-History:The...

, and many other castles were built. The commotes of Talacharn and Penrhyn became English-speaking at the time, but was subsequently re-cymricised (except for the coastal part of Talacharn). The rest of the cantref remained Welsh

Welsh language

Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

 speaking, as it continues today.

At the time of the Acts of Union, the cantref was split between the newly-formed counties, when Efelfre became part of Narberth

Narberth (hundred)

thumb|200px|right|Pembrokeshire showing Narberth HundredThe Hundred of Narberth was a hundred in Pembrokeshire, Wales. It was formed by the Act of Union of 1536 from parts of the pre-Norman cantrefs of Penfro and Cantref Gwarthaf...

 hundred, Pembrokeshire

Pembrokeshire

Pembrokeshire is a county in the south west of Wales. It borders Carmarthenshire to the east and Ceredigion to the north east. The county town is Haverfordwest where Pembrokeshire County Council is headquartered....

 and the rest became part of Carmarthenshire

Carmarthenshire

Carmarthenshire is a unitary authority in the south west of Wales and one of thirteen historic counties. It is the 3rd largest in Wales. Its three largest towns are Llanelli, Carmarthen and Ammanford...

: Amgoed, Penrhyn, Peuliniog, Talacharn, Ystlwys and part of Derllys became Derllys hundred, while Elfed and the rest of Derllys were combined with Emlyn Uwch Cuch

Emlyn

Emlyn was one of the seven cantrefi of Dyfed, an ancient district of Wales. It subsequently became part of Deheubarth in around 950. It consisted of the northern part of Dyfed bordering on the River Teifi...

 and Gwidigada commote of Cantref Mawr to form Elfed

Elvet (hundred)

Elvet was a hundred, a geographic division, in the traditional county of Carmarthenshire, Wales....

hundred.