William Mounsey CB was a British officer of the Royal Navy. He served during the American Revolutionary, the French Revolutionary and the Napoleonic Wars, rising to the rank of Captain.

HMS Jason was a 36-gun fifth-rate Penelope-class frigate, launched in 1800. She served the entirety of her career in the English Channel, mostly in the frigate squadron of Commodore Charles Cunningham. Serving off the coast of France, especially around Le Havre and Cherbourg, she captured several French privateers and recaptured a British merchant ship in a cutting out expedition. Having only been in commission for around fifteen months, Jason was wrecked off the coast of St Malo on 21 July 1801. Her crew were saved and later exchanged, and in August her wreck was burned to prevent the French from rescuing it.