Goat Rock Beach, Sandy beach at Russian River mouth in Sonoma Coast State Park, California.

Goat Rock Beach is a crescent-shaped sandy beach at the mouth of the Russian River in Sonoma Coast State Park. The shoreline extends from the river outlet to a large rock formation that connects to the mainland by a narrow strip of land.

Goat Rock Beach is a sub-unit of Sonoma Coast State Beach, owned and managed by the State of California. The Russian River, Sonoma County's largest watercourse by flow and length, reaches the Pacific at the beach's northern end, while the flat-topped greywacke sea stack called Goat Rock anchors the southern end, joined to the mainland by a narrow isthmus now used as a parking area. The San Andreas Fault runs roughly parallel to the shoreline just offshore.

The beach marks the mouth of the Russian River, Sonoma County's largest watercourse, and the river's summer sandbar separates it from the Pacific until winter flows breach it. Harbor seals use the northern section, cut off by the river, for pupping. Visitors are asked to keep 50 yards from hauled-out seals and sea lions.

Two separate parking areas provide access to different sections of the beach: one near the river mouth and another below the main rock formation. Exploring both areas at low tide reveals more of the beach and offers varied perspectives of the landscape.

The dark gray pebble stretch immediately north of Goat Rock, about 100 metres long, contrasts with the coarser brown and gray sands elsewhere on the beach. The sand itself shifts every year, and winter storms can strip one to three feet of land from the bluffs.