Six ships of the Royal Navy have been named HMS Amethyst, whilst another was planned:
- HMS Amethyst (1793) was a 36-gun fifth-rate frigate, originally the French Perle captured in 1793 and wrecked in 1795.
- HMS Amethyst (1799) was a Penelope-class 36-gun fifth rate launched in 1799 and wrecked in 1811.
- HMS Amethyst (1844) was a Spartan-class 26-gun sixth rate launched in 1844 and sold in 1869 for use as a cable vessel.
- HMS Amethyst (1871) was an Amethyst-class screw corvette launched in 1871 and sold in 1887.
- HMS Amethyst (1903) was a Topaze-class cruiser launched in 1903 and scrapped in 1920.
- HMS Amethyst (F116) was a modified Black Swan-class sloop launched in 1943. She was later designated as a frigate, was involved in the Yangtze Incident in 1949 and was broken up in 1957.
- HMS Amethyst was to have been a River-class minesweeper. She was renamed HMS Waveney before being launched in 1983, and was sold to the Bangladeshi Navy in 1994, being renamed Shapla.