The River Loughor (/ˈlʌxər/) (Welsh: Afon Llwchwr) in Carmarthenshire, Wales has its source at an underground lake at the Black Mountain and emerges at the surface from Llygad Llwchwr which translates from the Welsh as "eye of the Loughor". It flows past Ammanford and Hendy in Carmarthenshire and Pontarddulais in Swansea. The river divides Carmarthenshire from Swansea for much of its course and it separates Hendy from Pontarddulais at the point where the river becomes tidal. The Loughor meets the sea at its estuary near the town of Loughor where it separates the south coast of Carmarthenshire from the north coast of the Gower Peninsula. Among its tributaries is the River Amman, which joins the Loughor near Pantyffynnon. The area of the catchment is some 262 km2 (101 sq Miles).
In the 18th century, the river was a noted salmon and sea trout river. Fish from the river was then carried on ponies to be sold at Swansea Market. The fishing declined in the 19th century due to increasing pollution from industrialisation.
Carmarthenshire County Council is currently undertaking studies into the possibility of constructing a barrage across the River Loughor upstream from the Loughor bridges.
The Loughor Estuary (aka Burry inlet or Burry estuary, from the small Burry River which enters on the Gower side near its mouth) is the region of the waterway below the road and rail bridges at Loughor, where it turns abruptly from a southerly to a westerly direction towards Carmarthen Bay. The Afon Lliw empties into the estuary just below the Loughor bridges. This region almost completely empties at low tide, exposing extensive sandy areas supporting a thriving cockle industry.