Tromsø is a city and municipality in Troms county, Norway. The administrative centre of the municipality is the city of Tromsø. Outside Norway, Tromso and Tromsö are alternative spellings of the city. Tromsø town has a population of 64,376 as of 1 January 2016. The m… Tromsø is a city and municipality in Troms county, Norway. The administrative centre of the municipality is the city of Tromsø. Outside Norway, Tromso and Tromsö are alternative spellings of the city. Tromsø town has a population of 64,376 as of 1 January 2016. The most populous town north of it is Alta, Norway, with a population of 14,272 .