Hardangervidda (Hardanger Plateau) is a mountain plateau (Norwegian: vidde) in central southern Norway, covering parts of Vestland, Vestfold og Telemark, and Viken counties. It is the largest plateau of its kind in Europe, with a cold year-round alpine climate, and one of Norway's largest glaciers, Hardangerjøkulen, is situated here. Much of the plateau is protected as part of Hardangervidda National Park. Hardangervidda is a popular tourist and leisure destination, and it is ideal for many outdoor activities.
The plateau is the largest peneplain (eroded plain) in Europe, covering an area of about at an average elevation of . The highest point on the plateau is the Sandfloegga, which reaches a height of .
The landscape of the Hardangervidda is characterised by barren, treeless moorland interrupted by numerous pools, lakes, rivers and streams. There are significant differences between the west side, which is dominated by rocky terrain and expanses of bare rock, and the east side, which is much flatter and more heavily vegetated. The climate also varies between the two sides: it is considerably wetter on the west side than on the east, with over per year recorded in some parts. The prominent peak of Hårteigen is visible across much of the plateau.
Much of the Hardangervidda's geology is extremely ancient. The rolling fells of the Hardangervidda are the remnants of mountains that were worn down by the action of glaciers during the ice ages. The bedrock is mainly of Precambrian and Cambro-Silurian origin.
The area of Hardangervidda was once part of the Sub-Cambrian peneplain before it was thrust over by the nappes of the Caledonian orogeny in Paleozoic times. Much later, in the Miocene epoch, the modern flatness of Hardangervidda took form as a peneplain formed at sea level. Then in Early Pliocene times Hardangervidda and the whole of southern Scandinavian Mountains were uplifted more than thousand meters.
The whole of the Hardangervidda is above the tree line.