South Wales was the southernmost region of Wales.
It included the cities of Cardiff (TV: The Stolen Earth) and Swansea, (TV: The Categories of Life) both of which were located on the southern coast, overlooking the Bristol Channel. (PROSE: Another Life, TV: The Categories of Life) Other notable towns in South Wales included Aberdare, Abergavenny, Abertillery, Ammanford, Barry, Bridgend, Carmarthen, Ebbw Vale, Gorseinon, Llanelli, Llantwit Major, Maesteg, Merthyr Tydfil, Mountain Ash, Neath, Pontypool, Porthcawl, Port Talbot, Pyle and Rhymney. (TV: The Categories of Life)
When the Daleks transported Earth (along with 26 other planets) to the Medusa Cascade, it caused an earthquake-like effect on the entire planet. In the Torchwood Hub, Gwen Cooper stated that the whole of South Wales must have felt that, but Ianto Jones discovered the true extent, remarking, "Little bit bigger than South Wales..." (TV: The Stolen Earth) Blon Fel-Fotch Passameer-Day Slitheen noted that the entire South Wales coast would fall into the sea and no-one would notice. (TV: Boom Town)
In the 2010s, South Wales was targeted by a tsunami caused by the Committee, who manipulated Norton Folgate and Yvonne Hartman from Pete's World. Tyler Steele managed to convince Yvonne to try to stop the crisis, which she managed to do for Newport but not for Cardiff. (AUDIO: Eye of the Storm)