Fort Michilimackinac was an 18th century French, and later British, fort and trading post in the Great Lakes of North America. Built around 1715, it was located along the southern shore of the strategic Straits of Mackinac connecting Lake Huron and Lake Michigan, at the northern tip of the lower peninsula of the present-day state of Michigan in the United States. The site of the fort in present-day Mackinaw City is a National Historic Landmark and is now preserved as an open-air historical museum.

The primary purpose of the fort was not military, but rather as a link in the French trading post system that stretched from the Mississippi River through the Illinois Country to the St. Lawrence River. The fort served as a supply depot for traders in the western Great Lakes.

The French had first established a presence in the Straits of Mackinac in 1671 when Father Marquette established the Jesuit St. Ignace Mission at present-day St. Ignace. In 1683, they augmented the mission with Fort de Buade. In 1688 they established a mission at Sault Ste. Marie. In 1701, Sieur de Cadillac moved the French garrison to Fort Detroit and closed the mission. By 1715, however, the French built Fort Michilimackinac to re-establish a presence along the Straits of Mackinac, with several modifications and expansions to the palisade walls over the decades.