Triangle Marsh is a wetland of the San Francisco Bay, situated at the base of Ring Mountain at the north end of the Tiburon Peninsula in Marin County, California.^[1]

Archaeological Pecked curvilinear nucleated petroglyphs, and recovery on Ring Mountain, hold significant evidence of Native American habitation and likely proof that early Miwok peoples exploited marine resources from Triangle Marsh.^[2]

The 31-acre (130,000 m²) property is owned by the Marin branch of the National Audubon Society who restored upland and wetland habitats there with funding from a variety of sources. Federal endangered species, including the clapper rail and salt marsh harvest mouse, live in the Marsh.