Cynfarch Oer was probably a 6th century king of the Sub-Roman

Sub-Roman Britain

Sub-Roman Britain is a term derived from an archaeological label for the material culture of Britain in Late Antiquity: the term "Sub-Roman" was invented to describe the potsherds in sites of the 5th century and the 6th century, initially with an implication of decay of locally-made wares from a...

 realm of Rheged

Rheged

Rheged is described in poetic sources as one of the kingdoms of the Hen Ogledd , the Brythonic-speaking region of what is now northern England and southern Scotland, during the Early Middle Ages...

, believed to be located in north-west England

England

England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

 and south-west Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

.

Next to nothing is known about Cynfarch. He appears in the Old Welsh

Old Welsh language

Old Welsh is the label attached to the Welsh language from about 800 AD until the early 12th century when it developed into Middle Welsh. The preceding period, from the time Welsh became distinct from the British language around 550, has been called "Primitive Welsh".Many poems and some prose...

 pedigrees of the Brython

Brython

The Britons were the Celtic people culturally dominating Great Britain from the Iron Age through the Early Middle Ages. They spoke the Insular Celtic language known as British or Brythonic...

ic 'Men of the North

Hen Ogledd

Yr Hen Ogledd is a Welsh term used by scholars to refer to those parts of what is now northern England and southern Scotland in the years between 500 and the Viking invasions of c. 800, with particular interest in the Brythonic-speaking peoples who lived there.The term is derived from heroic...

' as the son of the equally obscure Meirchion Gul

Meirchion Gul

Meirchion Gul was probably a late 5th century king of Rheged, a Brythonic realm in the area of sub-Roman known as the Hen Ogledd .Next to nothing is known about Meirchion, although his epithet means the Lean...

 (Marcianus the Lean) and father of the slightly better documented Urien Rheged

Urien

Urien , often referred to as Urien Rheged, was a late 6th century king of Rheged, an early British kingdom of the Hen Ogledd . His power and his victories, including the battles of Gwen Ystrad and Alt Clut Ford, are celebrated in the praise poems to him by Taliesin, preserved in the Book of Taliesin...

. His name was well remembered however and his family were known as the 'Cynferchyn' in his honour. His unflattering epithet Oer probably means '(the) Unwelcoming' (literally 'cold').

It is assumed that Cynfarch ruled in Rheged before Urien. Hence the apparent 'Rheged' placename at Dunragit

Dunragit

Dunragit is a village on the A75, between Stranraer and Glenluce in Dumfries and Galloway in south-west Scotland. It grew up around the west gate of Dunragit House, an 18th century three-storey four-bay country house. It expanded considerably in the 1950s...

 near Stranraer

Stranraer

Stranraer is a town in the southwest of Scotland. It lies in the west of Dumfries and Galloway and in the county of Wigtownshire.Stranraer lies on the shores of Loch Ryan on the northern side of the isthmus joining the Rhins of Galloway to the mainland...

 and tales of March ap Meirchion

Mark of Cornwall

Mark of Cornwall was a king of Kernow in the early 6th century. He is most famous for his appearance in Arthurian legend as the uncle of Tristan and husband of Iseult, who engage in a secret affair.-The legend:Mark sent Tristan as his proxy to fetch his young bride, the Princess Iseult, from...

 (or Cun-march ap Meirchion) in the same area. He may also have been a participant in the Battle of Arfderydd

Battle of Arfderydd

The Battle of Arfderydd was fought, according to the Annales Cambriae, in 573. The opposing armies are variously given in a number of Old Welsh sources, perhaps suggesting a number of allied armies were involved...

 in 573.