Thornton State Beach, State beach along coastal cliffs in San Mateo County, United States.

Thornton State Beach is a coastal park with steep cliffs rising above the Pacific Ocean and sandy coves below. The landscape shows natural erosion patterns and forms a rugged transition between land and water.

The area takes its name from Robert S. Thornton, one of the first European settlers from the 1850s who established himself as a blacksmith in the region. The coastal location shaped settlement patterns and economic use of the area in its early years.

The beach carries the name of Robert S. Thornton, a blacksmith from Rhode Island who arrived in the San Francisco area in 1851 and was the area's first white settler. The 58-acre park was established in 1955 and named after him.

The 58-acre park sits on the Pacific coast of Daly City, reached from the end of John Daly Boulevard where it meets Skyline Boulevard. The beach lies below steep cliffs, so check landslide conditions before descending. Fog and cold wind are common in summer, and the park was closed from 2009 until it fully reopened in late 2021.

The park covers 58 acres and was established in 1955. Landslides forced it to close in 2009, and it was fully open again by late 2021. The name honours Robert S. Thornton, a blacksmith from Rhode Island who arrived in the San Francisco area in 1851.