Thomas Pownall (bapt. 4 September 1722 (New Style) – 25 February 1805) was a British colonial official and politician. He was governor of the Province of Massachusetts Bay from 1757 to 1760, and afterwards sat in the House of Commons from 1767 to 1780. He travelled widely in the North American colonies prior to the American Revolutionary War, opposed Parliamentary attempts to tax the colonies, and was a minority advocate of colonial positions until the Revolution.
Classically educated and well-connected to the colonial administration in London, Pownall first travelled to North America in 1753, and spent two years exploring the colonies before being appointed Lieutenant Governor of New Jersey in 1755. He became governor of Massachusetts in 1757 after helping engineer the recall of longtime Governor William Shirley. His administration was dominated by the French and Indian War (called the "Seven Years War" in England) in which Pownall was instrumental in raising Massachusetts provincial militia for the war effort. He opposed military interference in colonial administration, including attempts to quarter British troops in private homes, and had a generally positive relationship with the colonial assembly.
Returning to England in 1760, he continued to be interested in colonial affairs, publishing widely read materials on conditions in the colonies, including several editions of ''The Administration of the Colonies''. As a Member of Parliament he regularly advocated for colonial positions without much success, but supported the war effort once the Revolutionary War began. In the early 19th century he became an early advocate of the reduction or removal of trade barriers, and the establishment of a solid relationship between Britain and the United States. Several writers have proposed that Pownall was Junius, a pseudonymous writer of letters critical of British governmental practices.
John Adams wrote, "Pownall was the most constitutional and national Governor, in my opinion, who ever represented the crown in this province."