Her Majesty's Yacht "Britannia", also known as the Royal Yacht Britannia, is the former royal yacht of the British monarch, Queen Elizabeth II, in service from 1954 until 1997. She was the 83rd such vessel since King Charles II acceded to the throne in 1660, and is the second royal yacht to bear the name, the first being the racing cutter built for the Prince of Wales in 1893.

The Britannia was built at the shipyard of John Brown & Co. Ltd in Clydebank, West Dunbartonshire. She was launched by Queen Elizabeth II on 16 April 1953, and commissioned on 11 January 1954. The ship was designed with three masts: a 133-foot (41 m) foremast, a 139-foot (42 m) mainmast, and a 118-foot (36 m) mizzenmast. The top aerial on the foremast and the top 20 feet (6.1 m) of the mainmast were hinged to allow the ship to pass under bridges.

During her 43-year career, the yacht travelled more than a million nautical miles around the globe. Now retired from royal service, "Britannia" is permanently berthed at Ocean Terminal, Leith in Edinburgh, Scotland. It is a popular visitor attraction with over 300,000 visits each year.

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