Eidfjord is a municipality in Vestland county. The municipality borders in the north towards Ulvik, and in the south and west towards Ullensvang. Across the Hardangervidda, the municipality borders in the east on Hol and Nore and Uvdal municipalities in Viken county. Until the merger of Vestland county, Eidfjord belonged to Hordaland county. Eidfjord is located in the landscape Hardanger and includes the inner part of the Eidfjord, the valleys within, and the northwestern part of the Hardangervidda. The Eidfjord is an arm of the Hardangerfjord, and the Simadalsfjord is again an arm of the Eidfjord.

The municipality has an unknown code of inhabitants (2020). The town of Eidfjord is the municipality's administration center, and has 541 inhabitants as of 1 January 2020. The town, the municipality's only, is also called Nedre Eidfjord, to separate it from the densely populated area Øvre Eidfjord at the southern end of Eidfjordvatnet.


Names and weapons
The municipality is named after Eidfjorden (Norse Eiðafjörðr). The first part was genitive of the name of the farm Eiðar, the old church area. The name of the farm came from Eið, which referred to the property between the fjord and Eidfjordvatnet.

The property itself consists of two plains, Lægreid (the low property) and Hæreid (the high property).

The municipal coat of arms is on a blue background a silver reindeer antler. It was approved in 1984. The first known settlers in this area were hunters who hunted reindeer. Reindeer have been important to the people here for many centuries. The municipal coat of arms also symbolizes the rivers that run from mountains to fjords.

90% of the municipality's area is over 900 meters above sea level, and most of this is on the Hardangervidda. Many of the mountains are over 1,600 masl, and the highest point is on Hardangerjøkulen, on the border with Ulvik, 1,863 meters above sea level.

The part of the high mountain plateau located in Eidfjord municipality is the more hilly part. While the plateau has a general height of 1,100–1,200 masl, the mountains around Hardangerjøkulen extend over 1,700 masl. From the plateau, the mountains plunge into the valleys and into the fjord, creating a dramatic landscape. The southern part of the municipality is located in Hardangervidda National Park, and the northern and eastern part is located in Skaupsjøen / Hardangerjøkulen landscape conservation area.

Valleys and watercourses
The largest watercourses in Eidfjord are Bjoreio and Veig, which both flow into Eidfjordvatnet and further out into Eidfjorden through Eio.

Veig flows down into Valursdalen through Valursfossen, and further down into Hjølmadalen before Eidfjordvatnet. Berdølo flows in from Berastøldalen at the top of Hjølmadalen. The watercourse is protected from power development.

Bjoreio flows through Bjoreidalen and Sysendalen, and then down into Måbødalen through Vøringsfossen. The tributaries Leiro and Kjeldo flow into Sysenvatnet, which is dammed with Sysendammen. From Bjoreio, Sysenvatnet and the tributary Isdølo in Isdalen, water is fetched through tunnels to Sima power plant.

The river Sima flows through Simadalen and out into Simadalsfjorden. Across the valley is Rembesdalsvatnet, which is one of several reservoirs for the Sima power plant. Skytjedalselva flows down into Simadalen through Skytjefossen.