Pinnacle Rock, 600 feet (180 m), is a traprock mountain peak located 10 miles (16 km) southwest of Hartford, Connecticut, in the towns of Farmington and Plainville.

Pinnacle Rock, popular as an outdoor recreation destination in the metropolitan Hartford area, is known for its clifftop scenic vistas, unique microclimate ecosystems, rare plant communities, and as a seasonal raptor migration path.

HA-67 was a Nike 1B defensive missile base which operated from 1956 through March 1961 on the Plainville side of the rock near Loon Lake, southeast of the summit.

Subsequent faulting and earthquake activity tilted the strata, creating the cliffs and ridgeline of Pinnacle Rock.

Hot, dry upper slopes, cool, moist ravines, and mineral-rich ledges of basalt talus produce a combination of microclimate ecosystems on the mountain that support plant and animal species uncommon in greater Connecticut.