Streptanthus howellii is an uncommon species of flowering plant in the mustard family known by the common name Howell's jewelflower.

It is a perennial herb producing a hairless, often waxy-textured stem up to 70 or 80 centimeters in maximum length.

The ephemeral basal leaves have fleshy oval blades with smooth or toothed edges, borne on petioles.

Each has a calyx of purple sepals under a centimeter long with purple-tipped yellow petals emerging from the tip.

This rare plant is threatened by wildfire suppression; it would be more common if its habitat were allowed its natural fire regime.