Astragalus wetherillii is a species of flowering plant in the legume family known by the common name Wetherill's milkvetch. It is native to Colorado and Utah in the United States. This perennial herb grows from a taproot and a caudex which yields several stems. The stems are partly purplish or reddish in color and are finely hairy. The leaves are green, without the silvery hairs of some other Astragalus. Each leaf is up to 10 centimeters long and is made up of up to 15 leaflets. The flowers are white or lavender-tinted and roughly a centimeter long. The fruit is a legume pod with a single chamber inside. It is green and sometimes purple-speckled.