Six ships of the Royal Navy have been named HMS Cornwall after the county of Cornwall in England. Cornwall's motto is unus et omnes (one and all).
- HMS Cornwall (1692), was an 80-gun third-rate ship of the line, served in the wars of the Grand Alliance, the Spanish Succession and the Austrian Succession, broken up in 1761
- HMS Cornwall (1761), was a 74-gun third-rate, served in the Seven Years War and the American Revolutionary War until broken up in 1780
- HMS Cornwall (1812), was a 74-gun third-rate, served in the Napoleonic Wars, in 1868 she was renamed Wellesley and served as a school ship until broken up in 1874
- HMS Cornwall (1902), was a Monmouth-class armoured cruiser, served in World War I and fought at the battle of the Falkland Islands and at the Dardanelles
- HMS Cornwall (56), launched in 1926, was a County-class heavy cruiser, served in World War II and was sunk by Japanese air attack during the Indian Ocean raid in 1942
- HMS Cornwall (F99), launched in 1985, is a Type 22 Batch 3 frigate
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