The Caldicot and Wentloog Levels are two areas of low-lying estuarine alluvial wetland and intertidal mudflats adjoining the north bank of the Severn Estuary, either side of the River Usk estuary near Newport in south east Wales. They are also known collectively as the Monmouthshire Levels or Gwent Levels, and the name Wentloog is sometimes spelled Wentlooge in official publications.
The Caldicot Level lies to the southeast of Newport between the River Usk and River Wye and consists of 17,500 acres (71 km2). It is home to Newport Wetlands Reserve. The Wentloog Level lies to the southwest between the River Usk and Rhymney River and consists of 8,500 acres (34 km2).
The levels are formed from tidal deposits and alluvium, which have been recurrently inundated and reclaimed from the Severn Estuary by humans since Roman times. They have been patterns of settlement, enclosure and drainage systems belonging to successive periods of use, and are extremely rich archaeologically, with finds from the Mesolithic, Bronze Age and Iron Age periods.
They are an important wetland resource. Parts have been designated as Sites of Special Scientific Interest. They are registered as a Historic Landscape of Outstanding Historic Interest in Wales.