Belvedere Lagoon is an artificial lagoon in the Marin County, California community of Belvedere on San Francisco Bay. Narrow strips of land separate it from Richardson Bay (to the northwest) and Raccoon Strait. Rising above the lagoon on higher ground is Ring Mountain on the Tiburon Peninsula. This area of Ring Mountain is notable for its archaeological resources of extant Native American petroglyphs as well as a great biodiversity of California native plants.
The lagoon is owned and maintained by the Belvedere Lagoon Property Owner's Association. The lagoon is not accessible by boat from the San Francisco Bay, and no public access is provided. Until somewhat late in the 20th century houseboats were present in Belvedere Lagoon.