A new species of Antennaria (Asteraceae: Gnaphalieae) fromthe Klamath Mountains of northern California, A. sawyeri, isdescribed and illustrated. The species appears to be endemic to serpentine soils (i.e. soils derived from ultramafic parent materials such as peridotite or serpentinite) in subalpine habitats in the Trinity Alps and is very narrowly distributed, occupying scattered sites within a two square kilometer range near Red Mountain and Middle Peak. It is an amphimictic (dioecious) diploid (2n = 28) and a member of the circumboreal Pulcherrimae subgroup within Antennaria. The closest relative of A. sawyeri is probably A. lanata, which does not occur in California. In addition to its restriction to serpentine soils, it is primarily distinguished from A. lanata by the shape of its basal leaf apices and lack of flags on the lower and middle cauline leaves. It is readily distinguished from the other Oregon/California serpentine endemic, A. suffrutescens, by its polycephalous capitulescences and adaxially pubescent leaves. Updated keys to Antennaria are provided.