Robert Dinwiddie (1693 – 27 July 1770) was a British colonial administrator who served as lieutenant governor of colonial Virginia from 1751 to 1758, first under Governor Willem Anne van Keppel, 2nd Earl of Albemarle, and then, from July 1756 to January 1758, as deputy for John Campbell, 4th Earl of Loudoun. Since the governors at that time were largely absentee, he was the de-facto head of the colony for much of the time.
Dinwiddie's actions as lieutenant governor are commonly cited as precipitating the French and Indian War. He wanted to limit French expansion in Ohio Country, an area claimed by the Virginia Colony and in which the Ohio Company, of which he was a stockholder, had made preliminary surveys and some small settlements.
In 1753, Dinwiddie learned the French had built Fort Presque Isle near Lake Erie and Fort Le Boeuf, which he saw as threatening Virginia's interests in the Ohio Valley. He sent an eight-man expedition under George Washington to warn the French to withdraw. Washington, then only 21 years old, made the journey in midwinter of 1753-54. The French refusal to withdraw set the stage for the events that took place at Fort Necessity.