Streptanthus callistus is a rare species of flowering plant in the mustard family known by the common name Mount Hamilton jewelflower.

[1] It is endemic to Santa Clara County, California, where it is known from only about five occurrences around Mount Hamilton.

It is an annual herb producing a small stem up to 8 or 9 centimeters tall with a bristly base.

The fertile flowers on the lower raceme have calyces of bristly purple-green sepals under a centimeter long with flaring purple petals at the tip.

The sterile flowers at the top of the raceme have narrow, elongated, hairless purple sepals.