Leirfjord is a municipality in Nordland county, Norway. It is part of the Helgeland traditional region. The administrative centre of the municipality is the village of Leland. Other villages in Leirfjord include Bardalssjøen and Sundøy. The large Helgeland Bridge is partly located in the municipality, connecting it to Alstahaug Municipality and the town of Sandnessjøen.
The 465 km2 municipality is the 213th largest by area out of the 356 municipalities in Norway. Leirfjord is the 264th most populous municipality in Norway with a population of 2,257. The municipality's population density is 5 PD/km2 and its population has increased by 7.1% over the previous 10-year period.
The municipality of Leirfjord was established on 1 July 1915 when it was separated from the municipality of Stamnes. Initially, the municipality had 2,003 residents. In 1945, a small part of Nesna Municipality (population: 45) was merged into Leirfjord. During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964, Leirfjord Municipality (population: 1,936) was merged with the parts of Nesna Municipality located south of the Ranfjorden (population: 580) and the parts of Tjøtta Municipality on the island of Alsta (population: 180) to form a new, larger municipality of Leirfjord.