The spectacle, which attracts visitors from around the globe, takes place in Lerwick on the last Tuesday of January each year.
People dressed as Vikings march through the streets of the town to recreate its ancient Viking past, in a tradition dating back to the 19th century.
The procession is led by the Guizer Jarl, or chief guizer, and culminates in a replica longboat being set alight.
This year the boat is decorated in the distinctive green and white hoops of Celtic at the behest of Guizer Jarl John Nicolson, a supporter of the football club.
Volunteers are responsible for the building of the galley boat and the production of more than 1,000 torches.
Those taking part in the festival spend the night visiting a host of celebrations in halls around the town.
Shetland and neighbouring Orkney were ruled by the Norse for about 500 years until they became part of Scotland in 1468.
The festival stems from the 1870s when a group of young local men wanted to put new ideas into Shetland’s Christmas celebrations.