South Wales (Welsh: De Cymru) is an area of Wales bordered by England and the Bristol Channel to the east and south, and Mid Wales and West Wales to the north and west. The most densely populated region in the south-west of the United Kingdom, it is home to around 2.1 million people and includes the capital city of Cardiff (population approximately 324,800), as well as Swansea and Newport. The Brecon Beacons national park covers about a third of South Wales, containing Pen y Fan, the highest mountain south of Snowdonia.

The extent of South Wales is loosely defined, but it is generally considered to be the area surrounding the M4 motorway, including the historic counties of Glamorganshire and Monmouthshire and sometimes extending westwards to include south Carmarthenshire and south Pembrokeshire. In the western extent, from Swansea westwards, local people would probably recognise that they lived in both South Wales and in West Wales — there is considerable overlap in these somewhat artificial boundaries. The northern border is particularly ill-defined, but the A40 may be a good approximation whilst others consider the more southerly Heads of the Valleys Road as the boundary.

Wales ⁱ/ˈweɪlz/ (Welsh: Cymru;Welsh pronunciation: [ˈkəm.rɨ] ( listen)) is a country that is part of the United Kingdom and the island of Great Britain,bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km² (8,023 sq mi). Wales has over 1,200 km (750 mi) of coastline, including its offshore islands; the largest, Anglesey (Ynys Môn), is also the largest island in the Irish Sea. Wales is largely mountainous, with its highest peaks in the north and central areas, especially in Snowdonia (Eryri), which contains Snowdon (Yr Wyddfa), its highest summit.