The town has a population of 22,838 (1 January 2024),[2] and is an important traffic portal with its ferry connections to Gothenburg in Sweden.

[3]: 5–6 The first mention of a settlement is in a letter dated 13 March 1572 found in the Danish chancery letterbooks.

[3]: 8–9 During the Great Nordic War from 1700 to 1721 the town saw a rise in activity as travellers to Norway embarked from here as the route over Sweden was cut.

[3]: 11–12 Due to its advantageous proximity to the entrance to the Baltic Sea, Frederikshavn has historically been a naval base of some strategic importance.

In 1627 under Kejserkrigen, Melchior von Hatzfeldt troops built a Sconce north of the fishing village.

[5]: 95  In 1712 the Battle of Fladstrand was fought in the nearby sea between Swedish and Danish naval forces.

[3]: 11–12  From the middle of the 18th century the military importance of the citadel was dwindling and some of the fortifications and building was disposed of.

The first artificial harbour was constructed from 1808 to 1810 due to the war and after several years of strong promotion of the local merchant Frantz Übersax.

[4]: 61–62  The harbour directorate (Danish: Kanal-, havne- og fyrdirektionen) argued that it was a strategic place for a harbour and giving the town market town status and legalising the current activities would help with the upkeep.

Between 1974 and 1976 the engineering firm Kampsax and the local contractor Trigon encased the tower in concrete and moved it 270m along teflon rails to its current location.

The project was delayed when a storm broke a retaining wall between Christmas and New Year 1975 filling the new dry dock with water and causing the base beneath the tower to collapse.

[9]: 221 Stena Line operated a ferry service from Frederikshavn to Oslo, Norway from 1979 to March 14, 2020.

[13][14] The Oslo route was reopened by DFDS Seaways on June 25, 2020 by the ferries traveling to and from Copenhagen which began stopping in Frederikshavn.

Today there is still activity at the large ship building area, with many small companies renting space there.

In summer 2008, the unemployment rate, like the rest of Denmark, fell to a minimum low record of approximately 2%.

As with many provincial municipalities around the world, some of its young people leave to large urban cities.

However, the municipality is currently engaged in many innovative projects which are attracting tourists and aim to retain population.

Frederikshavn is currently beginning a transition to make it the first medium-sized city/large town in the world to rely exclusively on renewable energy resources for power, including transportation and cars.

Frederikshavn was in the late 19th century the dominant harbour for large fishing vessels in Denmark.

[28][9]: 13  The site of the former Danyard was over the next 20 years transformed into a business park and the activity gradually went from manufacturing to service.

[32][28] The expansion makes it possible to receive larger ships and offshore installations, handle more bulk material and a flexible area for projects.

[34] Most of the quay and hinterland areas in the first phase have been leased by Louisiana-based Modern American Recycling Services for an 11-year period.

[28] When the second phase is complete the total area of the harbour will be 950,000 square metres (10,200,000 sq ft).

It is home to Danish navy 1st Squadron and Naval Operational Logistic Support Structure, OPLOG FRH.

[40] The also town has a number of smaller marinas (listed in order from north to south): Frederikshavn practices twinning on the municipal level.