Whitesands Bay (Welsh: Porth-Mawr) shown as Whitesand Bay on some maps, is an EEC award winning, Blue Flag standard, wide sandy beach in St Bride’s Bay in the Pembrokeshire Coast National Park, United Kingdom. The beach is located about two miles west of the city of St David’s and about one mile south of St David’s Head and has been described as the best surfing beach in Pembrokeshire and one of the best tourist beaches in the world.The area to the North east of the bay is dominated by a large rocky outcrop, 594 ft at its highest point, known as Carn Llidi. The Pembrokeshire Coastal Path passes alongside the bay giving access in the north to the secluded bays of Porthlleuog and Porthmelgan which are only accessible on foot, and the rugged coastal scenery of St David’s Head and the Pembrokeshire Coastal Park. To the south the coastal path leads to Porthselau and St Justinian’s, with views across the Ramsey Sound to Ramsey Island. There are a number of megalithic burial chambers, stone hut circles and iron age enclosures to be seen in the vicinity of Carn Llidi and St David’s Head.
It is said that St. Patrick had his vision to convert Ireland to Christianity here and set sail from the bay in the fifth century. The ruins of a celtic chapel, dedicated to St Patrick, are located under a mound by the car park just to the east of the bay, at what is is thought to have been the embarcation point for pilgrims to St David’s Cathedral.