HMS Unicorn is a British fifth-rate frigate of 46 guns.
Construction began in February 1822 at the Royal Dockyard, Chatham, and the frigate was launched in February 1822. Carrying 46 guns, she was 151.6 feet (46.2 m) long. She was one of the most successful classes of frigates of the Leda type, one of the best of her generation, which was itself based on the designs of the French frigate Hebe captured in 1782. This class of ships included HMS Shannon, which captured the American frigate USS Chesapeake and HMS Trincomalee, which is the oldest frigate still afloat in Britain ahead of HMS Unicorn.
The hull of HMS Unicorn is still afloat in the dock at Dundee Harbour in Scotland.