Micropus amphibolus is a species of flowering plant in the aster family known by the common name Mount Diablo cottonseed. It is endemic to California, where it is known from the San Francisco Bay Area and nearby mountains, growing in open, rocky habitat. It is an annual herb similar in appearance to its relative, the "Q-tips". It produces one or more small, erect stems coated thinly in wispy, webby fibers. The inflorescence is a spherical flower head a few millimeters wide which resembles a tiny cotton boll since the flowers and maturing fruits are very woolly.