Astragalus iodanthus is a species of flowering plant in the legume family, Fabaceae, known by the common names Humboldt River milkvetch and violet milkvetch. It is native to the western United States, where its range includes California, Idaho, Nevada, Oregon, and Utah. It grows on hills and in valleys in barren sandy and volcanic soils in habitat such as sagebrush. There are two varieties of this species: