George Johnstone was a Royal Navy officer who saw service during the War of the Austrian Succession, the Seven Years' War and the American War of Independence, rising to the rank of post-captain and serving for a time as commodore of a British naval squadron. In a multifaceted career he was also a member of parliament, a director of the East India Company, a member of the Carlisle Peace Commission and the first Governor of West Florida from 1763 until 1767.

The Battle of Porto Praya was a naval battle that took place during the American Revolutionary War on 16 April 1781 between a British squadron under Commodore George Johnstone and a French squadron under the Bailli de Suffren.