Streptanthus glandulosus subsp. niger is an endangered subspecies of flowering plant within the family Brassicaceae. Like other genus members, this herb has wavy petal margins with perimeter calluses that discourage larval herbivory. This plant is endemic to the Tiburon Peninsula of Northern California, and occurs at elevations below 150 m on serpentine grasslands. The common name for this subspecies is Tiburon jewelflower or black jewelflower. This annual herb blooms in May and June and displays dark purple sepals. The etymology of this genus scientific name derives from the Greek word streptanthus, meaning twisted flower, with reference to the notable wavy margins of the petals. The subspecies name niger relates to the color of the seeds being black, although an alternate account cites the dark color of the petals as the source of the appellation.

Tiburon is an incorporated town in Marin County, California. It is located on the Tiburon Peninsula, which reaches south into the San Francisco Bay. It shares a ZIP code (94920) with the smaller incorporated city of Belvedere, which occupies the southwest part of the peninsula and is contiguous with Tiburon. Tiburon is bordered by Corte Madera to the north and Mill Valley to the west, but is otherwise mostly surrounded by the bay. Besides Belvedere and Tiburon, much of the peninsula is unincorporated, including portions of the north side and the communities of Strawberry and Paradise Cay.