Mendocino Headlands State Park, Coastal state park in Mendocino, United States.

Mendocino Headlands State Park covers 347 acres of undeveloped seaside bluffs and islets around the town of Mendocino, plus two beaches and the 7,334-acre Big River Unit along both banks of the Big River. The headlands are rocky bluffs overlooking the Pacific; west and north of town they widen into coastal prairie crossed by Heeser Road and footpaths. The Big River Unit holds 1,500 acres of wetlands and the longest undeveloped estuary in Northern California.

Mendocino Headlands State Park began operation in 1974 after several years of citizen concern and discussion about possible blufftop development. The Big River Unit was added on July 30, 2002, after the Mendocino Land Trust led a group of donors, nonprofits and agencies to raise over 25 million dollars and buy the land from the Hawthorne Timber Company. That unit includes remnants of the historic Mendocino Lumber Company sawmill.

Ford House Museum, at the east end of Main Street on the headlands side, serves as the park headquarters and visitor center. It shows videos on the town's logging boom and the migration of the gray whales, plus a scale model of Mendocino as it was in 1890. Guided walks on the headlands start here, and the Mendocino Music Festival takes place on the headlands in July.

Big River Beach sits at the mouth of the Big River south of town, reached by footpaths from the east end of Main Street behind the Presbyterian Church or from a parking lot on the inland side of State Route 1. Portuguese Beach, a smaller cove at the west end of Main Street, is reached by a footpath along the headlands and a staircase down to the sand. The coves below the headlands to the north are accessible only by boat.

The Big River Unit was bought from the Hawthorne Timber Company in 2002 for over 25 million dollars, raised by the Mendocino Land Trust and partner donors and agencies. Its 7,334 acres hold 1,500 acres of wetlands and remnants of the historic Mendocino Lumber Company sawmill. Canoes and kayaks can paddle eight miles of forested river.