Erysimum insulare is a species of wallflower known by the common name island wallflower. It is endemic to coast of southern California, including the Channel Islands, where it grows on coastal bluffs and sand dunes. This is a perennial herb or subshrub producing a branching, erect stem 5 to 60 centimeters tall. It is lined with many hairy leaves which are linear to widely lance-shaped. The longest leaves near the base of the stem may be up to 15 centimeters long. The top of the stem is occupied by a raceme flower cluster of many bright yellow to yellow-orange flowers. The fruit is a silique up to 10 centimeters long. There are two subspecies of this plant, most individuals belonging to ssp. suffrutescens. The rare ssp. insulare is limited to three of the Channel Islands.