The Hardanger Line (Norwegian: Hardangerbana or Hardangerbanen) was a 27.45-kilometre (17.06 mi) railway between Voss and Granvin in Hordaland, Norway. The line connected to the Bergen Line in Voss and ran to the Hardangerfjord and the district of Hardanger. Construction started in 1921, but the line did not open until 1 April 1935. Owned and operated by Norwegian State Railways (NSB), passenger transport was provided by three NSB Class 64 electric multiple units. They remained in use until 1985 when passenger transport was terminated. All transport ceased in 1988, and 21 kilometres (13 mi) of the line was demolished in 1991. The 3 kilometres (2 mi) from Voss to Palmafoss is still intact and is owned by the Norwegian National Rail Administration. The line featured six stations, fourteen halts and four tunnels and was one of Norway's steepest railways. It was NSB's first line to be electrified. The line was known as the Granvin Line (Granvinbanen) until February 1936. In 2016, Palmafoss established an emergency freight terminal and the tracks were re-established.

The Hardanger Line ran 27.45 km (17.06 mi) from Voss to Granvin in Hardanger. From Voss to Skjervet, the line ran in relatively flat terrain, with easy construction. Along this section, the route followed what is now Norwegian National Road 13. At Skjervet, the two split; the gradient increased towards Nesheim and the topography became more difficult. On this section there were four tunnels named Skjervet Tunnel I to IV, the longest being 1,101 m (3,612 ft). The line was built on a shelf between the two longest tunnels. Later, the tunnel was extended from 630 m (2,070 ft) to also include that portion in the tunnel. The railway ran on the west side of the River Granvinvatnet from Skjervet, while the road ran on the east side.

The Hardanger Line was built with a minimum curve radius of 180 m (590 ft) and a maximum gradient of 4.5 per cent and was built with standard-gauge tracks weighing 25 kg/m (50 lb/yd), later increased to 30 kg/m (60 lb/yd). In 1980, the 3 kilometres (2 mi) section from Voss to Palmafoss had a permitted axle load of 18 tonnes (18 long tons; 20 short tons) and a maximum speed of 40 km/h (25 mph). From Palmafoss to Granvin, the permitted axle load was 12 tonnes (12 long tons; 13 short tons) and the maximum speed was 50 km/h (31 mph). The system had stations with buildings at Voss, Palmafoss, Mønshaug, Skjervet, Nesheim and Granvin. In addition, there were halts at Haugamo, Kinne, Bjørgum, Mala, Dalsleitet, Flatlandsmo, Såkvitno, Selland and Kolanes.

Granvin is a port on the Hardangerfjord and was the center for freight transport in Hardanger. Hardanger is dominated by a small number of large industrial companies, primarily smelters, which were responsible for more than 80 percent of the line's cargo volume. While Hardanger in the 1980s had a population of 40,000, Granvin had a population of 1,000 and was the smallest municipality in Hardanger. Granvin served as a ferry hub for services by Hardanger Sunnhordlandske Dampskipsselskap (HSD), and in 1980 there up to two daily services with the local ferry services in Hardanger, in addition to fast ferries to both Bergen and Stavanger. Buses operated to Granvin from Norheimsund and Kvanndal.

The line and power system is intact for 3 km (1.9 mi) from Voss to Palmafoss and is maintained by the Norwegian National Rail Administration. From there to Skjervet, the line has been asphalted and is used as a hiking and cycle path. The section from Skjervet to Nesheim is disused now, although it has been proposed as a road. The hiking and cycle path continues from Nesheim, although the right-of-way no longer exists on the last kilometre before Granvin. The station buildings at Nesheim and Granvin are still standing, but the ones at Palmafoss, Mønshaug and Skjervet have been demolished.

In 2016, Palmafoss established an emergency freight terminal for the Bergen line. If the Bergen Line is closed, freight can be transferred to trucks at Palmafoss. At the same time the tracks were renovated and re-established between Voss and Palmafoss.

During construction of the Voss Line from Bergen to Voss, there was a proposal to extend the line from Voss to Granvin on the Hardangerfjord. The plans were again taken up to consideration with the construction of the Bergen Line, but also this time the plans were scrapped. Some people wanted the line to be a tramway and when it was passed by the Parliament of Norway on 12 July 1919; the plans incorporated some elements of a tramway, giving the line a lower standard than the main line. The railway was to be built in an electrified form and construction started in 1921. However, there was a lack of engineers, forcing a slow pace. On 5 November 1923, parliament passed the final plans for the railway and the pace of construction was accelerated.

In 1927, Minister of Labour Worm Hirsch Darre-Jenssen of the Conservative Party stopped the work on the railway, however, stating that time had run out and that a road should be built there instead. By then, 5 million kr had been invested and parliament decided that construction should continue. However, Darre-Jenssen convinced Hordaland County Council to make a statement against the Hardanger Line, the Flåm Line and the Namsos Line, without this stopping construction. In 1931, parliament reconsidered the electrification of the line, and there was consensus for electrification. The Hardanger Line opened on 1 April 1935 and became NSB's first line to be electrified at the time of opening. In February 1936, the line changed name from the Granvin Line to the Hardanger Line.