The Nordland Line (Norwegian: Nordlandsbanen, Urban East Norwegian: [ˈnûːrlɑnsˌbɑːnn̩]) is a 729-kilometer (453 mi) railway line between Trondheim and Bodø, Norway. It is the longest in Norway and lacks electrification. The route runs through Trøndelag and Nordland counties, carrying a combination of commuter, long-haul passenger and freight trains. From Trondheim Central Station to Steinkjer Station the line is most heavily used, with hourly services by the Trøndelag Commuter Rail. There are three branch lines—the Stavne–Leangen Line at Leangen Station, the Meråker Line at Hell Station and the Namsos Line at Grong Station.

The section from Trondheim to Hell opened on 22 July 1882. The next section, initially the Hell–Sunnan Line, opened in stages between 1902 and 1905. The line was lengthened to Snåsa Station on 30 October 1926 and then to Grong on 30 November 1929. Construction continued in a slow pace northwards, but was accelerated by the Wehrmacht after the 1940 occupation. The line was built through most of Helgeland and opened in seven stages to Dunderland Station in the next five years. The line then had to be brought up to standards before continuing northwards. It opened to Røkland Station in 1955, to Fauske Station in 1958 and to Bodø Station on 1 February 1962.

Traditionally the Nordland Line was defined as running from Hell to Bodø, but the National Rail Administration has officially classified it as running from Trondheim Central Station to Bodø, a distance of 728 kilometers (452 mi). This makes it the longest railway line in Norway. It is single track, standard gauge, but not electrified. Centralized traffic control is installed south of Mosjøen, with partial automatic train control. GSM-R is installed on the whole line. The Nordland Line is owned and maintained by the Norwegian National Rail Administration.

From Trondheim the line runs largely following the Trondheimsfjord to Steinkjer Station, traveling through the districts of Stjørdalen and Innherred. At Hell Station, 31.54 km (19.60 mi) from Trondheim, the Meråker Line branches off. North of Steinkjer (125.50 km or 77.98 mi) the line follows the east shore of Snåsavatnet until Snåsa Station (181.64 km or 112.87 mi), passing into the district of Namdal. At Grong Station (219.54 km or 136.42 mi) the line intersects with the Namsos Line. It continues up the valley through an inland route and passes into the district of Helgeland. There it reaches a summit of 320 meters (1,050 ft) above sea level at Majavatn Station (321.74 km or 199.92 mi) before descending back to sea level near Mosjøen Station (406.01 km or 252.28 mi). The line continues along a rugged section often hugging the sides of fjords until Mo i Rana Station (497.98 km or 309.43 mi).

From Mo the line runs up the Dunderland Valley at a 1.2% gradient. From Dunderland Station (543.03 km or 337.42 mi) the line climbs at a 1.8% gradient for 38.5 kilometers (23.9 mi) onto the Saltfjellet mountain plateau. It reaches its highest elevation just south of Stødi Station (581.46 km or 361.30 mi), at 680 meters (2,230 ft) above mean sea level, about 1.8 kilometers (1.1 mi) after passing the Arctic Circle. The line then descends for the next 40 kilometers (25 mi) at a 1.8% gradient until reaching almost sea level at Rognan Station (647.76 km or 402.50 mi), by which time it has reached the district of Salten. The section onward to Finneid Station (671.08 km or 416.99 mi) has steep terrain and the line hugs the mountainside, frequently entering tunnels. From Fauske the line heads west to Bodø Station.

A committee to look into building a railway northwards from Trondheim was established in 1870. The goal was to build a railway which connected to Jämtland, Sweden. Similar investigations were carried out on the Swedish side of the border. An early alternative to build via Verdal was discarded. The line was at first estimated to cost 4.7 million Norwegian krone and the line built with a narrow gauge. Shares in the railway company were offered for sale in 1871, of which NOK 1.2 million was bought by Trondheim Municipality. The Parliament of Norway rejected the line the same year, although it resulted in a local railway committee being established. Legislation to build the line was passed by Parliament on 2 May 1872. The state would receive shares in the company equal to their monetary contribution. In 1873, the Parliament of Sweden voted to build a narrow gauge railway from Torpshammar to the Norwegian border, where it would connect to the Sundsvall–Torpshammar Line.

By 1874, Swedish authorities had decided that all railways should be built in standard gauge, and the Parliament of Norway chose to change their configuration to the same gauge in 1874, increasing estimated costs from NOK 4.7 to 8.9 million. In Trondheim, the existing Trondhjem–Støren Line terminated at a station at Kalvskinnet. This was a cul-de-sac station, and to allow the two lines to interconnect, a new station was built at Brattøra, costing NOK 1.4 million.

The river of Stjørdalselva created a barrier just north of Hell, and it would be cheaper to make the line go on the south shore of the river down to Hegra. However, the major population center was located at Stjørdalshalsen, on the north shore of the river. Locally, there were many protests against the line bypassing such a large town, but the cost of the bridge made parliament choose the southern alternative. This gave residents in Stjørdal a considerably longer route to the train, since they had to cross the river to get access to the railway. This decreased the railway's ability to compete with the steam ships and thus the overall profitability of the line.