Eidfjord is a municipality in Vestland county, Norway. The municipality is located in the traditional district of Hardanger. The administrative centre of the municipality is the village of Eidfjord, where the majority of the municipal population lives. The other major population centre in the municipality is the village of Øvre Eidfjord.

Eidfjord is situated at the end of the Eid Fjord, an inner branch of the large Hardangerfjorden. The village of Eidfjord is a major cruise ship port of call and has plans to install a power connection big enough for ships to turn off their engines . Eidfjord has several tourist sites, like the Sima Power Plant which is built into the mountain itself, the Måbødalen valley, and the Vøringsfossen waterfall which has a free fall of 182 metres (597 ft). Large parts of the Hardangervidda (Europe's largest mountain plateau) are located in Eidfjord. The Hardangervidda Natursenter, a visitors centre and museum for Hardangervidda National Park, is located in Øvre Eidfjord.

The 1,498-square-kilometre (578 sq mi) municipality is the 57th largest by area out of the 356 municipalities in Norway. Eidfjord is the 337th most populous municipality in Norway with a population of 962. The municipality's population density is 0.7 inhabitants per square kilometre (1.8/sq mi) and its population has increased by 1.1% over the previous 10-year period.

In 2016, the chief of police for Vestlandet formally suggested a reconfiguration of police districts and stations. He proposed that the police station for Ullensvang og Eidfjord be closed.

The parish of Graven (later spelled "Granvin") was established as a municipality on 1 January 1838 (see formannskapsdistrikt law). This large municipality/parish included two annexes: Ulvik and Eidfjord. On 1 January 1859, Ulvik became the main parish, making Granvin and Eidfjord annexes to Ulvik, and the name of the large municipality was changed from Graven to Ulvik.

On 1 May 1891, the municipality of Ulvik was divided into three separate municipalities: the western part became Graven Municipality (population: 1,331) and the southeastern part became the new Eidfjord Municipality (population: 1,018). This left a much smaller Ulvik Municipality in between the two new municipalities. In 1895, a small part of Eidfjord (population: 3) was transferred back to Ulvik Municipality.

Eidfjord existed as a municipality from 1891 until 1964 when a major municipal merger took place as a result of municipal reform in Norway due to the Schei Committee. Eidfjord Municipality (population: 983), most Kinsarvik Municipality (population: 1,513), and Ullensvang Municipality (population: 2,358) were all merged into one large Ullensvang Municipality. This merger was not well-liked by the population of Eidsfjord, and so on 1 January 1977, part of the merger was undone, and the area of the "old" Eidfjord Municipality (population: 1,223) was separated to form its own municipality once again.

On 1 January 2022, the roughly 7-square-kilometre (2.7 sq mi) Ytre Bu area of Ullensvang Municipality (population: 24) was transferred to the neighboring Eidfjord Municipality.