HMS Unicorn is a surviving sailing frigate of the successful Leda class, although the original design had been modified by the time that the Unicorn was built, to incorporate a circular stern and "small-timber" system of construction. Listed as part of the National Historic Fleet, Unicorn is now a museum ship in Dundee, Scotland, United Kingdom. She is the oldest ship in Scotland, one of the oldest ships in the world, and one of the last intact warships from the age of sail.

The Leda-class frigates, were a successful class of forty-seven British Royal Navy 38-gun sailing frigates constructed from 1805 to 1832. Based on a French design, the class came in five major groups, all with minor differences in their design. During their careers, they fought in the Napoleonic Wars and the War of 1812. Forty-five of the 47 were eventually scrapped; two still exist: HMS Trincomalee and HMS Unicorn.