Muckle Flugga lighthouse was built by Thomas and David Stevenson in 1854, originally to protect ships during the Crimean War. It stands on a small rocky island north of Unst in the Shetland Islands, Scotland and is the most northerly lighthouse in Britain.

The name comes from Old Norse, Mikla Flugey, meaning "large steep-sided island". The original name was "North Unst", but in 1964 that was changed to "Muckle Flugga".

Muckle Flugga lighthouse stands 20m (64 feet)high, has 103 steps to the top. The light beam flashes white every 20 seconds, with a nominal range of 35 km (22 miles).

According to local folklore, Muckle Flugga and nearby Out Stack were formed when two giants, Herma and Saxa, fell in love with the same mermaid. They fought over her by throwing large rocks at each other, one of which became Muckle Flugga. To get rid of them, the mermaid offered to marry whichever one would follow her to the North Pole. They both followed her and drowned, as neither one could swim.

During the Crimean war the government urged the commissioners to set up a light on Muckle Flugga to protect Her Majesty's ships. A temporary lighthouse, a structure 15 m (50 feet)high and 61 m (200 feet) above sea level, was built and lit on 11 October 1854. It was thought to be high and safe enough to withstand the elements, but when winter storms began, waves broke heavily on the tower and burst open the door to the living quarters so that the keepers had no dry place to sit or sleep. Plans were made for a higher and more permanent lighthouse, but there were still disagreements about where to locate it, Muckle Flugga or Lamba Ness. The orders to start the work on the new Muckle Flugga tower were finally given in June 1855 and it was first lit on 1 January 1858.

Thomas Stevenson and his brother, David, built fourteen of the lighthouses around the Scottish coast. Thomas was the father of Robert Louis Stevenson, Scotland's most famous novelist and author of 'Treasure Island'. It is known that he visited Muckle Flugga on 18 June 1869 with his father, and it is thought that as a result the island of Unst became his inspiration for 'Treasure Island'.

Muckle Flugga was one of the few lighthouses in Scotland which had a separate shore station that served as accommodation for the lighthouse keepers, when they were off duty (similar to Sule Skerry and its shore station in Stromness, Orkney). The shore station was sold off when the lighthouse was automated in March 1995. It now hosts the Hermaness Visitor Centre at the entrance to the neighbouring Hermaness Nature Reserve, which is managed by Scottish Natural Heritage.