Which mountain's Welsh name is Yr Wyddfa?

The mountain whose Welsh name is Yr Wyddfa is Snowdon.

Snowdon, or Yr Wyddfa, is the highest mountain in Wales, rising to approximately 1,085 metres in North Wales. It stands within Snowdonia National Park, known in Welsh as Eryri, and is also the highest peak in the British Isles south of the Scottish Highlands.

The English name Snowdon comes from Old English elements meaning “snow hill.” Yr Wyddfa has a much older Welsh history: its earliest recorded form appears in 1284, and the name is linked with ideas of a height, promontory or burial cairn.

Welsh legend says the summit is the burial place of Rhitta Gawr, a giant defeated by King Arthur. The modern naming convention can cause confusion: many Welsh authorities now favour Yr Wyddfa, but Snowdon remains the familiar English name and identifies the same mountain. Tryfan, Pen y Fan and Cadair Idris are separate Welsh peaks.