Pilostyles thurberi is a species of flowering plant known by the common names Thurber's stemsucker and Thurber's pilostyles. It is native to the southwestern United States and northern Mexico, where it grows in desert and woodland. It has been recorded from Arizona, Texas as well as Mexico.
It is a tiny parasitic plant, only a few millimeters long, which lives in the stem tissues of its host plants, species of legume shrubs, often of genus Psorothamnus, especially Emory's indigo bush or dyebush (Psorothamnus emoryi). It has no roots, leaves, or chlorophyll, obtaining its water and nutrients from the host. It grows completely within its host until it blooms, sending tiny flowers through the surface of the host plant. It is dioecious, with male and female individuals producing one type of flower each. Both types are brown or maroon and no more than 2 millimeters across, appearing as specks on the stem of the host plant. The bloom usually occurs in January, but sometimes as early as November. The female flower swells slightly as the fruit capsule develops within, and each may hold over 100 seeds, which are minute.