George Johnstone (1730-1787) was a British naval officer and member of Parliament.
George Johnstone was the fourth son of Sir James Johnstone, 3rd Baronet of Westerhall, Dumfries, and his wife Barbara Murray, the oldest sister of the literary patron Patrick Murray, 5th Lord Elibank. He was a younger brother of William Johnstone (later Johnstone Pulteney).
He began his career at sea in the Merchant Navy, then entered the Royal Navy in 1746. Shortly after his promotion to Lieutenant in 1755, Johnstone was court martialed for "insubordination and disobedience" however, his record of gallantry in combat taken into account, he was given a reprimand in 1757. He was promoted Captain in 1762, and Commodore in 1763.
Appointed colonial governor of West Florida (present day Panhandle west of the Mississippi River) in November 1763, Johnstone would serve in West Florida for four years. During this time, he began a long-term relationship with Martha Ford, by whom he had the following illegitimate issue, all of whom he supported:
He returned to Great Britain in 1767 entering Parlaiment. He served as MP for Cockermouth, 1768-74; Appleby, 1774-80; Lostwithiel, 1780-84; Ilchester, 1786-87, taking an independent line. During his time in Parliament his conduct was reportedly "his shameless and scurrilous utterances" and in December 1770, after publicly insulting Lord George Germain for "cowardice in battle", he eventually fought Germain in a duel, although ending inconclusively.
A member of the Carlisle Peace Commission during the American Revolution, the Secibd Continental Congress refused to negotiate with the British delegation in 1778, accusing Johnstone of bribery. During his time in America, he met up with his first cousin, Patrick Ferguson. However, in exchange for politically supporting Lord Sandwich, Johnstone was given command of a naval squadron off the coast of Portugal in May 1779. Patrolling the South Atlantic, Johnstone met with moderate success capturing the French 44-gun frigate Artois before successfully defending against Vice Admiral Pierre Andre de Suffren de Saint Tropez at the Battle of Porto Praya off the coast of Praia, Cape Verde on April 16, 1781. Although he planned to attack the Cape of Good Hope, he later decided on returning to England.
In 1782, in Lisbon, Johnstone married Charlotte Dee, by whom he had one son, John Lowther Johnstone (1783-1811). Following the war, Johnstone served as director of the East India Company for two years until his resignation due to poor health (he was suffering from throat cancer) in 1785, when he retired from public life. He died in 1787. His son John later succeeded his uncle William Johnstone Pulteney as 6th Baronet of Westerhall.