| Fort Willoughby | |
| Location: | Hassel Island, U.S. Virgin Islands |
| Map Type: | Caribbean |
| Map Size: | 250 |
| Type: | Fortification |
| Coordinates: | 18.1933°N -64.5549°W |
| Built: | 1777-1780 |
| Materials: | Stone |
| Site Area: | Hassel Island Historic District |
| Used: | No |
| Ownership: | U.S. Virgin Island's government |
| Open To Public: | Yes |
Fort Willoughby (previously Prince Frederik's Battery) is a historic fort on Hassel Island in the U.S. Virgin Islands.
The fort was built in 1777-1780 by the Danish, who originally named it Prince Frederik's Battery.[1] At that time, Hassel Island was part of the Danish West Indies. During their first occupation of the Danish West Indies (1801-1802), the British took over the fort and renamed it Fort Willoughby.[2] The British used the fort again during their second occupation of the Danish West Indies (1807-1815).
Originally, the fort consisted of parapet wall, gun platform, barracks, magazine, and storeroom, as well as kitchen, cistern, and privy.[3] Today, the remains of the fort consist of the remnants of the magazine, barracks, and cistern.[4]
Fort Willoughby is protected within the Virgin Islands National Park.[5] It contributes to the Hassel Island Historic District,[6] which has been listed on the National Register of Historic Places since 1976.[7]