Calochortus monanthus
 Calochortus monanthus is a species of flowering plant in the lily family known by the common names single-flowered mariposa lily and Shasta River mariposa lily. It is presumed extinct having been collected and documented once over a century ago and never found again. The single known specimen was collected by botanist Edward Lee Greene from a meadow on the banks of the Shasta River near Yreka California in June of 1876.