Waun Mawn (Welsh for "peat moor") is a megalithic site in the Preseli Mountains of Pembrokeshire, Wales.

[4] This tract of moorland sits on the southern slopes of the 339 m (1,112 ft) hill top of Cnwc yr Hŷdd ("cock of the corn"), just to the north of the broad east-west ridge of the Preseli range.

[7] Following soil dating of the sediments within the postulated stone holes, via optically stimulated luminescence (OSL), it has been argued, by Parker Pearson, that the circle of stones was built c. 3400–3200 BC and then, before 2120 BC, was disassembled, dragged across land and reassembled at Stonehenge in Wiltshire, some 140 mi (230 km) distant.

[14][15] In a 2024 study published in The Holocene, Brian John re-examined the geological and archaeological evidence from the site, and concluded that the "lost circle" of standing stones had never existed, and that there was no evidence to demonstrate a link with Stonehenge.

He concluded that there had been considerable "interpretative inflation" at the site, driven by a desire to show a Stonehenge connection.