Ring Mountain, Mountain summit in Tiburon, Marin County, California, US

Ring Mountain is a 184-metre-high plateau on the Tiburon Peninsula in Marin County, California. Its twin summits are made of serpentinite, and the upper slopes are a serpentinite-matrix mélange containing blocks of blueschist, eclogite, amphibolite and greenschist. The Phyllis Ellman Loop Trail, about 2 miles long, crosses the preserve.

Ring Mountain takes its name from George E. Ring, a dairyman who served as a Marin County Supervisor from 1895 to 1903. The land had passed to the Reed family in 1834, and their descendants ended cattle and horse grazing in the mid-1960s before selling over 400 acres to a developer. That sale set off a years-long campaign, and The Nature Conservancy bought over 300 acres in 1981 and 1984, transferring the land to Marin County in 1995.

The Coast Miwok people left petroglyphs on the rocks here, marking their presence and traditions in the region before European settlement. These engravings show how long indigenous communities knew and used this place.

The climb is moderate and trails are well marked, making access easier for visitors with different abilities. Visitors should wear sturdy shoes, as the serpentine rock creates uneven surfaces.

The Tiburon mariposa lily (Calochortus tiburonensis) grows on Ring Mountain and nowhere else on Earth, in the thin serpentine soil near the summit. The mountain also holds the Tiburon jewelflower and Tiburon paintbrush, and about 330 other plant species have been counted here.