Alyssum desertorum is a species of flowering plant in the mustard family known by the common name desert madwort. It is native to Europe and Asia, and it is found in parts of western North America as an introduced species and sometimes a weed. This is a hairy annual herb producing upright stems up to about 20 centimeters tall. It produces small yellowish flowers and round, notched fruits a few millimeters long. The seeds are winged and have embryonic roots.