HMS Castor was a 36-gun fifth rate frigate of the Royal Navy. Castor was built at Chatham Dockyard and launched on 2 May 1832. She was one of a two ship class of frigates, built to an 1828 design by Sir Robert Seppings, and derived from the earlier . The had a further 13 inches (33 cm) of beam to mount the heavier ordnance. Castor cost a total of £38,292, to be fitted for sea. Her first captain was Lord John Hay, and by September 1832 Castor was at Lisbon.