Lupinus rivularis is a species of lupine known by the common name riverbank lupine. It is native to western North America from southern British Columbia to northern California, where it is known mainly from coastal habitat. This is a robust, erect perennial herb or subshrub growing up to about a meter tall. The mostly hairless stem is thick, hollow, and reddish in color. Each palmate leaf is made up of 5 to 9 wide leaflets 2 to 4 centimeters long. The flower cluster is a raceme of many flowers sometimes arranged in whorls. The flower is light purple in color, often with white parts or shading. The fruit is a somewhat hairy legume pod up to 7 centimeters long which turns dark as it ages.