Snowdonia or Eryri (ɛrəri) is a mountainous region and national park in northwestern Wales.
Snowdonia contains every mountain in Wales over 3000 feet high, including the country's highest mountain, Snowdon (Yr Wyddfa, ). These peaks are all part of the Snowdon, Glyderau, and Carneddau ranges in the north of the region. South of them are the Moelwynion and Moel Hebog ranges.
The national park covers most of Gwynedd and the western part of Conwy County Borough, with an area of . This is much larger than the area traditionally considered Snowdonia, and in addition to the mountains above includes the Rhinogydd, Cadair Idris, and Aran ranges as well as the Dyfi Hills. It also includes most of the coast between Porthmadog and Aberdyfi. The park was the first of the three national parks of Wales to be designated, in October 1951, and the third in the UK after the Peak District and Lake District, which were established in April and May 1951 respectively. The park received 3.89 million visitors in 2015.
The name "Snowdon" means "snow hill" and is derived from the Old English elements "snāw" and "dūn", the latter meaning 'hill'. "Snowdonia" is simply taken from the name of the mountain.
The origins of Eryri are less clear. Two popular interpretations are that the name is related to eryr, "eagle", and that it means "highlands" and is related to the Latin oriri (to rise). Although 'eryri' is not any direct form of eryr (eagle), it is a plural form of eryr (upland).
Before the boundaries of the national park were designated, "Snowdonia" was generally used to refer to a smaller upland area of northern Gwynedd centred on the Snowdon massif. The national park covers an area more than twice that size, extending south into the Meirionnydd area.
This difference is apparent in books published before 1951. In George Borrow's 1907 Wild Wales he states that "Snowdon or Eryri is no single hill, but a mountainous region, the loftiest part of which [is] Y Wyddfa", making a distinction between the summit of the mountain and the surrounding massif.