The Dolaucothi Gold Mines (pronounced [ˌdɔlaiˈkɔθɪ]; Welsh: Mwynfeydd Aur Dolaucothi) (grid reference SN662403), also known as the Ogofau Gold Mine, are ancient Roman surface and underground mines located in the valley of the River Cothi, near Pumsaint, Carmarthenshire, Wales. The gold mines are located within the Dolaucothi Estate, which is owned by the National Trust.

They are the only mines for Welsh gold outside those of the Dolgellau gold-belt, and are a Scheduled Ancient Monument. They are also the only known Roman gold mines in Britain, although it does not exclude the likelihood that they exploited other known sources in Devon in South West England, north Wales, Scotland and elsewhere. The site is important for showing advanced Roman technology.

Archaeology suggests that gold extraction on this site may have started sometime in the Bronze Age, possibly by washing of the gold-bearing gravels of the river Cothi, the most elementary type of gold prospecting. Sextus Julius Frontinus was sent into Roman Britain in AD 74 to succeed Quintus Petillius Cerialis as governor of that island. He subdued the Silures, Demetae and other hostile tribes of Roman Wales, establishing a new base at Caerleon for Legio II Augusta and a network of smaller Roman forts approximately nine to twelve miles (fifteen to twenty kilometres) apart for his Roman auxiliary units. During his tenure, he probably established the fort at Pumsaint in west Wales, largely to exploit the gold deposits at Dolaucothi. Frontinus later restored the aqueducts of Rome and wrote the definitive treatise on 1st century Roman aqueducts, the two-volume De aquaeductu.

That gold occurred here is shown by the discovery of a hoard of gold ornaments in the 18th century. Objects found included a wheel brooch and snake bracelets, so named because they were soft enough to be coiled around the arm for display. All the objects are now held in the British Museum, and displayed in the Romano-British gallery. A sample of gold ore was found at the site by Henry De la Beche in 1844, confirming the presence of gold.

Evidence from the fortification (known as Luentinum from details given in Ptolemy's Geographia) and its associated settlement show that the Roman army occupied the fort from c. AD 78 to c. 125. However, coarse ware and Samian ware pottery recovered from a reservoir (Melin-y-Milwyr) within the mine complex show that activity at the mines continued until the late 3rd century at least. Since Ptolemy's map dates to about 150, it is likely that it continued being worked until the end of the 3rd century if not beyond.

The Romans made extensive use of water carried by several aqueducts and leats, the longest of which is about 7 miles (11 km) from its source in a gorge of the river, to prospect for the gold veins hidden beneath the soil on the hillsides above the modern village of Pumsaint. Small streams on Mynydd Mallaen, the Annell and Gwenlais, were used initially to provide water for prospecting, and there are several large tanks for holding the water still visible above an isolated opencast pit carved in the side of the hill north of the main site. The larger aqueduct from the Cothi crosses this opencast, proving the opencast to be earlier.

The water was stored in the tanks and then released suddenly, the wave of water sweeping away the soil to reveal the bedrock and any gold-bearing veins beneath. Pliny the Elder gives a dramatic account in his Naturalis historia of the method, possibly derived from his experiences in Spain. The method is known as hushing and survived in use until the 19th century in Britain, and into the 20th century in the goldfields of Africa. A not dissimilar method is used today in exploiting alluvial tin deposits, and is known as hydraulic mining. A smaller scale version of the same method is placer mining, and both may have been used to work alluvial placer deposits next to the river Cothi itself, judging by a large aqueduct which tapped the river a mile or so upstream, and enters the site at a low level compared with the other known aqueducts on the site. The water supply of the aqueducts was also used for washing crushed gold ore, and also possibly driving stamping mills for comminution of the ore (Lewis and Jones, 1969).

One of the first aqueducts was built at a high level on the east slope of Allt Cwmhenog and tapped a small stream about 2 miles (3 km) away. There is a large tank at its end, where it sweeps around the brow of the hill onto the west side of the ridge. A gold vein must have been discovered here, because there is a large opencast below the tank. Yet the larger and longer aqueduct (with a gradient of 1 in 800) taps the River Cothi about 7 miles (11 km) to the north-east and traverses the same opencast, so must be later in date.