HMS Thetis was a 36-gun fifth-rate frigate of the Royal Navy. After nearly a decade of service with the British, she was transferred to Prussia in exchange for two steam gunboats. She served with the Prussian Navy, the North German Federal Navy and the Imperial German Navy as a training ship until being stricken in 1871. Thetis was subsequently converted into a coal hulk and broken up in 1894–95.

The Prussian Navy, officially the Royal Prussian Navy, was the naval force of the Kingdom of Prussia from 1701 to 1867.