Lieutenant-General Patrick Sinclair (1736 – 31 January 1820) was a British Army officer and governor in North America. He is best remembered for overseeing the construction of Fort Mackinac on Mackinac Island in what was to become the U.S. state of Michigan.
Sinclair was born in Lybster, Scotland, and enlisted in the Army at about age 18. In 1758 he was commissioned Ensign in the 42nd Foot and was involved in the attack on Guadeloupe later that year.
By 1760, Sinclair was at Oswego, New York, where he was promoted Lieutenant, and involved in the Seven Years' War. His battalion were part of the force heading to attack Montreal under the command of Major-General Amherst. They captured a French brig near Fort Lévis and Sinclair was given command. After Amherst's force captured Fort Lévis in what became known as the Battle of the Thousand Islands, Sinclair was assigned to the area for the rest of Amherst's campaign. In 1761 he exchanged into the 15th Foot in order to stay in the area.
This contact with the Great Lakes attracted Sinclair and he was able to change his commission to serve on the lakes. He started out commanding ships on Lake Ontario but, in 1764, he was moved to the upper lakes where he served until 1767. In 1767, he was removed from active service at Fort Sinclair, which he had built in 1764 under orders from Colonel John Bradstreet.