Mynydd Llangyndeyrn is a Site of Special Scientific Interest (SSSI) in Carmarthen & Dinefwr, Wales. It is a hill reaching 263 metres (863 feet), which is a UK listed Marilyn. It is located west of Drefach and north of Pontyberem. The SSSI is approximately 1.3 miles (2.1 km) east-west and 0.3 miles (0.48 km) north-south, taking the approximate shape of a horns downwards shallow crescent. As well as a trig point there are the remains of several prehistoric round cairns, burial mounds and a standing stone probably dating to the Bronze Age (c.2300 BC - 800 BC) arranged along the ridge of Mynydd Llangynderyn.