Meirchion Gul was probably a late 5th century king 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...

, a Brythonic

Britons (historical)

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...

 realm in the area of 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...

 known as the Hen Ogledd

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...

(in the North of England today).

Next to nothing is known about Meirchion, although his epithet means the Lean. He appears in the Middle Welsh

Middle Welsh language

Middle Welsh is the label attached to the Welsh language of the 12th to 14th centuries, of which much more remains than for any earlier period. This form of Welsh developed from Old Welsh....

 genealogical text Bonedd Gwŷr y Gogledd

Bonedd Gwŷr y Gogledd

Bonedd Gwŷr y Gogledd is a brief Middle Welsh tract which claims to give the pedigrees of twenty 6th-century rulers of the Hen Ogledd , the Brythonic-speaking parts of southern Scotland and northern England. It is attested in a number of manuscripts, the earliest being NLW, Peniarth MS 45, which...

as the son of the equally obscure Gwrwst Lledlwm, a grandson of Coel Hen, and grandfather of renowned 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...

. He is assumed, like Urien, to have ruled Rheged, including Catterick

Catterick, North Yorkshire

Catterick , sometimes Catterick Village, to distinguish it from the nearby Catterick Garrison, is a village and civil parish in the Richmondshire district of North Yorkshire, England...

. His two sons appear at the head of two later dynasties. Cynfarch Oer

Cynfarch Oer

Cynfarch Oer was probably a 6th century king of the Sub-Roman realm of Rheged, believed to be located in north-west England and south-west Scotland.Next to nothing is known about Cynfarch...

 was Urien's father. Another son, Elidyr Lydanwyn (the Stout and Handsome), was the ruler of Rheged, accoriding to the Gwynedd version of Hywel Dda

Hywel Dda

Hywel Dda , was the well-thought-of king of Deheubarth in south-west Wales, who eventually came to rule Wales from Prestatyn to Pembroke. As a descendant of Rhodri Mawr, through his father Cadell, Hywel was a member of the Dinefwr branch of the dynasty and is also named Hywel ap Cadell...

's 'Welsh laws'. He was the father of Llywarch Hen

Llywarch Hen

Llywarch Hen was a 6th-century prince of the Brythonic kingdom of Rheged, a ruling family in the Hen Ogledd or 'Old North' of Britain...

.