Barnstable's Old Gaol is a historic colonial jail in Barnstable, Massachusetts. Built c.1690, it is the oldest wooden jail in the United States of America.

The jail was built by order of the Plymouth and Massachusetts Bay Colony courts. It served as the Barnstable County jail until c.1820, when a new stone jail was built. The structure, which held about six prisoners, was eventually attached to a barn. In 1968 it was rediscovered, separated from the barn, and moved 100 feet (30 m) onto the grounds of the Coast Guard Heritage Museum (located in the old Customshouse building) in Barnstable Village.

The building was listed on the National Register of Historic Places in 1971, and included in the Old King's Highway Historic District in 1987.

In 1716, the jail imprisoned Goody Hallett, the lover of pirate Samuel Bellamy, later known as the Witch of Wellfleet, as well as the two survivors of Sam Bellamy's flagship Whydah Gally which wrecked at Wellfleet, and the seven survivors of his consort ship Mary Anne which wrecked ten miles (16 km) south at Pochet Island. The jail house is considered one of the most haunted in America and is open to ghost tours at certain times of the year. It is believed to be haunted by Goody Hallett, who is said to also haunt the Expedition Whydah in Provincetown, as well as Lucifer Land (also called Goody Hallett's Meadow) which is a reference to the area of land at the top of the Wellfleet cliffs.

• National Register of Historic Places listings in Barnstable County, Massachusetts

• Official web site of caretakers
• Coast Guard Heritage Museum