Captain William Cayley (5 May 1742 – 3 January 1801) was a British Royal Navy officer.
The following year he was appointed captain of HMS Edgar and saw action against a Franco-Spanish fleet in the indecisive Battle of Cape Spartel.
[citation needed] In 1794 he was captain of the newly commissioned HMS Unicorn.
The following year he commissioned HMS Juste, a captured French ship, and commanded her for two months.
In December that year he was involved in an attack on the French fleet off Dominica.