Wentlooge, or Gwynllwg as it was called, was a kingdom within early Wales and later became a medieval Norman lordship.
Named after Gwynllyw, its 5th or 6th century ruler, it consisted of the coastal plain stretching between the Rhymney and Usk rivers, together with the hills to the north. It was traditionally regarded as part of the kingdom of Glamorgan (Morgannwg), rather than that of Gwent which extended only as far westwards as the River Usk. However, under the Laws in Wales Acts of 1535-42, the Wentlooge Hundred became included with those situated to the east, to form the new county of Monmouthshire, subsequently Gwent (1974), and now Newport (1996).
During the Roman occupation of Wales the largely marsh landscape was drained by digging ditches known as reens. The reens and remaining long thin field patterns are still evident today and are reminders of this earlier occupation. However the centuries that followed saw the gradual collapse of the sea walls and the reversion of most of the area to tidal saltmarsh.