Sulphur Springs Mountain (or Sulfur Springs Mountain) is a mountain in southwestern Solano County, California. The slopes can be accessed via hiking trails emanating from Blue Rock Springs Park in the city of Vallejo. Cinnabar deposits were extracted from this location in the early 1900s at Hastings Mine and St. John's Mine. Both mines are classified as medium priority mine from the standpoint of environmental oversight for California inactive mines. The highest peak on Sulfur Springs Mountain stands at an elevation of , and affords expansive views of the northern San Francisco Bay as well as the Napa River. The rock outcroppings which occur in the Sulphur Springs area are composed of basaltic lava; however, there are also serpentine outcrops, which soils are known to provide habitat for many rare and endangered species in Northern California.