Purgatory Chasm State Reservation is a protected state park in Sutton, Massachusetts. Located within the Blackstone Valley, the reservation is managed by the Massachusetts Department of Conservation and Recreation.

Previously owned by the Whitin Machine Works, Purgatory Chasm was declared a state park in 1919. The reservation is notable for its .25-mile-long (400 m), 70-foot-deep (21 m) chasm in granite bedrock with abrupt precipices and caves. Various theories have been proposed to account for the creation of the chasm. According to one source, it was created when glacial meltwater ripped out bedrock at the end of the last Ice Age.

Purgatory Chasm is open to the public, although the chasm proper is closed to hikers during the winter season because of icy hazards. There are 2 miles (3.2 km) of hiking trails, and rock climbing is allowed by permit. The reservation also includes picnic areas, a visitor center, and a playground.