Fort Sewall is a historic coastal fortification in Marblehead, Massachusetts. It is located at Gale's Head, the northeastern point of the main Marblehead peninsula, on a promontory that overlooks the entrance to Marblehead Harbor. Established in 1644, it is one of the oldest English coastal fortifications in the United States. Known for many years as either Marblehead Fort or the Fort on Gale's Head, it was given its present name in 1814 in honor of Massachusetts Supreme Judicial Court Chief Justice Samuel Sewall, who died in that year.
The fort was expanded in 1742, and a barracks and magazine were added in 1794 after the federal government took over the property. The fort was turned over to the town in 1922, and is now open as a public park. It was listed on the National Register of Historic Places in 1975.