Longyearbyen ('The Longyear Town') is the largest settlement and the administrative centre of Svalbard, Norway. It stretches along the foot of the left bank of the Longyear Valley and on the shore of Adventfjorden, the short estuary leading into Isfjorden on the west coast of Spitsbergen, the island's broadest inlet. Since 2002 Longyearbyen Community Council has had many of the same responsibilities as a Norwegian municipality, including utilities, education, cultural facilities, fire brigade, roads and ports. The town is the seat of the Governor of Svalbard. It is the world's northernmost settlement of any kind with more than 1,000 permanent residents. Since 2015 Arild Olsen has served as Mayor.

Known as Longyear City until 1926, the town was established by and named after American John Munro Longyear, whose Arctic Coal Company started coal-mining there in 1906. Store Norske Spitsbergen Kulkompani (SNSK) took over the mining operations in 1916, and still conducts mining. The German Kriegsmarine almost completely destroyed the town on 8 September 1943, but rebuilding took place after the Second World War. Historically, Longyearbyen was a company town, but most mining operations moved to Sveagruva during the 1990s, and production ceased in 2017 due to immense financial losses suffered by SNSK since 2014 due to market conditions. Meanwhile, the town has seen a large increase in tourism and research. This includes the arrival of institutions such as the University Centre in Svalbard, the Svalbard Global Seed Vault and Svalbard Satellite Station. Svalbard Airport and Svalbard Church serve the community.

The community council runs a number of cultural activities, such as a cinema, a youth club, a library and a gallery. The town's sports club is Svalbard Turn. Svalbardhallen is an indoor sport centre that includes a multi-sport hall large enough for handball or three badminton courts, a shooting range, a climbing wall and a 25-meter (82 ft) swimming pool. Svalbard Church of the Church of Norway has the entire archipelago as its parish. The congregational hall is 126 m² (1,360 sq ft) while the sitting room is 112 m² (1,210 sq ft). The church is built in half-timber. Svalbardposten is a weekly newspaper published on Friday. Printing takes place in Tromsø and the majority of subscribers live on the mainland. Icepeople, an alternative newspaper in English, is also published weekly. There are two museums in town, Svalbard Museum and the Spitsbergen Airship Museum. Solfestuka ("Sun Festival Week") takes place each year during the week surrounding March 8, the date sunlight is first visible in most of the town after the polar night that began the previous October (the first official sunrise is usually Feb. 16, but most of the town is still in shadow due to the surrounding mountains). Dark Season Blues has been held annually in October since 2003. Polarjazz has been held in late January/early February since 1998. Twenty residents of the town are members of the Liverbirds Svalbard and regularly meet in the Svalbar on match days during the winter months. Arctic Film Festival is a film festival which held annually in the city's screening venue, Kulturhuset. Longyearbyen is served by Arctic Outpost AM radio 1270.