The event in Lerwick is Europe's biggest fire festival, and takes place on the last Tuesday of January each year.
Around 900 costumed "guizers" wearing winged helmets, sheepskins and carrying axes and shields, marched through the streets of the town to recreate its ancient past.
The procession was led by the Guizer Jarl, or chief guizer.
Earlier in the day, a Junior Jarl elected from a local secondary school headed a mini-torchlight procession.
Later in the evening, the main procession snaked through the town streets to burn a traditional galley.
A host of volunteers are responsible for the building of the galley and the production of more than 1000 torches.
Work begins at the end of October to ensure that everything is ready for the celebrations, which often continue until 8am the following day, a public holiday on the island.
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.