Rhymney River in the context of "Bargoed"

Monmouthshire (/ˈmɒnməθʃər, ˈmʌn-, -ʃɪər/ MON-məth-shər, MUN-, -⁠sheer), also formerly known as the County of Monmouth (/ˈmɒnməθ, ˈmʌn-/ MON-məth, MUN-; Welsh: Sir Fynwy), was one of the thirteen counties of Wales that existed from 1536 until their abolition in 1974. Located in the south-east of Wales, on the border with England, its area now corresponds approximately to the present principal areas of Monmouthshire, Blaenau Gwent, Newport and Torfaen, and those parts of Caerphilly and Cardiff east of the Rhymney River.

The eastern part of the county was mainly agricultural, while the western valleys had rich mineral resources. This led to the area becoming highly industrialised with coal mining and iron working being major employers from the 18th century to the late 20th century. Its five largest towns were Newport, Cwmbran, Pontypool, Ebbw Vale and Abergavenny.

Old St Mellons (Welsh: Pentre Llaneirwg) is a village and community on the eastern edge of Cardiff, Wales. Lying to the east of the Rhymney River, it forms part of the historic county of Monmouthshire. It is separated from the modern St Mellons suburb by the main road to Newport – the Newport Road (B4487) – and which was formerly the A48 road.

The population of the community in 2011 was 2,367 and one of the smallest in Cardiff.