The St Lythans burial chamber (Welsh: siambr gladdu Lythian Sant) is a single stone megalithic dolmen, built around 6,000 BP (before present) as part of a chambered long barrow, during the mid Neolithic period, in what is now known as the Vale of Glamorgan, Wales.
St Lythans is around one mile (1.6 km) south of Tinkinswood burial chamber, a more extensive cromlech that it may once have resembled, constructed during the same period.
The site is on pasture land, but pedestrian access is allowed and is free, with roadside parking available for 2 – 3 cars about 50 yards (46 m) from the site.
The dolmen, which has never been fully excavated, is maintained by Cadw (English: to keep), the Welsh Historic Environment Agency.