Sir John Fastolf KG (1380 – November 5, 1459) is an English knight during the Hundred Years War, who has enjoyed a more lasting reputation as the prototype, in some part, of Shakespeare's Sir John Falstaff.

Many historians consider, however, that he deserves to be famous in his own right, not only as a soldier, but as a patron of literature, a writer on strategy and perhaps as an early industrialist.