Langvatnet (Lule Sami: Guhkesjávrre) is a lake that lies in the municipality of Sørfold in Nordland county, Norway. The 13.97-square-kilometre (5.39 sq mi) lake is located about 30 kilometres (19 mi) northeast of the village of Straumen, just north of Rago National Park and the border with Sweden.
Sørfold is a municipality in Nordland county, Norway. It is part of the traditional district of Salten. The administrative centre of the municipality is the village of Straumen. Other villages in the municipality include Leirfjordgården, Mørsvikbotn, Røsvika, Rørstad, Styrkesvik, and Øvre Kvarv. The municipality surrounds the Sørfolda fjord and stretches east to the border with Sweden.
The municipality of Sørfolden was established on 1 January 1887 when the old municipality of Folden was divided into Sørfolden and Nordfold-Kjerringøy. Initially, the population of Sørfolden was 1,946. The spelling was later changed to just Sørfold. On 1 January 1894, the Movik farm (population: 30) along the Sagfjorden was transferred from Nordfold-Kjerringøy to Sørfold.
On 1 January 1964, the Øyjord area (population: 81) was transferred to the neighboring municipality of Bodin. On the same date, the Mørsvikbotn area (population: 268) was transferred from Nordfold to Sørfold. On 1 January 1984, the Tårnvika and Øygården area (population: 22) along the Sørfolda fjord was transferred from Sørfold to Bodø.