Tromsø (Norwegian pronunciation: [ˈtrʊ̂msœ] ; Northern Sami: Romsa; Finnish: Tromssa; Kven: Tromssa; Swedish: Tromsö) is a city in Tromsø Municipality in Troms og Finnmark county, Norway. The city is the administrative centre of the municipality as well as the administrative centre of Troms county. The Diocese of Nord-Hålogaland and its Bishop are based at the Tromsø Cathedral in the city. The city is located on the island of Tromsøya which sits in the Tromsøysundet strait, just off the mainland of Northern Norway. The mainland suburb of Tromsdalen is connected to the city centre on Tromsøya by the Tromsø Bridge and the Tromsøysund Tunnel. The suburb of Kvaløysletta on the island of Kvaløya is connected to the city centre by the Sandnessund Bridge.
The 21.25-square-kilometre (5,250-acre) town has a population (2017) of 64,448 which gives the town a population density of 3,033 inhabitants per square kilometre (7,860/sq mi). The city centre (on Tromsøya) has a population of 38,980. The mainland borough of the city, Tromsdalen, has a population of 16,787 and the suburb of Kvaløysletta on the island of Kvaløya has a population of 8,681. The most populous town north of Tromsø in Norway is Alta, with a population of 15,094 (2017), making Tromsø a very large city for this vast rural northern part of Norway and the northernmost in the world with a population exceeding 20,000. It is the largest urban area in Northern Norway and the third largest north of the Arctic Circle anywhere in the world (following Murmansk and Norilsk).
The city's largest workplaces are the University of Tromsø (UiT) and University Hospital of North Norway. The Norwegian Polar Institute also has its headquarters in Tromsø. The Northern Lights Observatory was established in 1928, and two companies affiliated with the Kongsberg Gruppen collect satellite data from space using the observatory. The fishing industry is very important. Norway's Norges Råfisklag and Norges sjømatråd (seafood council) both have their headquarters in Tromsø. Sparebanken Nord-Norge also has its headquarters in the city. Furthermore, "Skatt nord", an agency of the Norwegian Tax Administration is based here too.
The city is warmer than most other places located on the same latitude, due to the warming effect of the Gulf Stream. Tromsø is even milder than places much farther south of it elsewhere in the world, such as on the Hudson Bay and in Far East Russia, with the warm-water current allowing for both relatively mild winters and tree growth in spite of its very high latitude.
The city centre of Tromsø contains the highest number of old wooden houses in Northern Norway, the oldest house dating from 1789. The city is a cultural centre for its region, with several festivals taking place in the summer. Torbjørn Brundtland and Svein Berge of the electronica duo Röyksopp and Lene Marlin grew up and started their careers in Tromsø. Noted electronic musician Geir Jenssen also hails from Tromsø.