Oak's Inn Military Reservation was a coastal defense site located in Misquamicut, Rhode Island in the town of Westerly, overlooking Misquamicut State Beach.

It was part of the Harbor Defenses of Long Island Sound.

Today, the site is a residential development.

The site had four "Panama mounts" (circular concrete platforms) for four towed 155 mm (6.1 inch) guns.

A battery of two 16-inch (406 mm) guns (Battery Construction Number 114) was proposed for this location but not built.