Eucephalus glabratus is a North American species of flowering plant in the family Asteraceae with the common names of smooth aster, smooth wayside-aster, and Siskiyou aster. It is a perennial herb up to 60 centimeters (24 inches) tall, with branching rhizomes. Stems and leaves are hairless or nearly so. One plant will usually produce 3–8 flower heads per stem. Each head has 0–4 violet ray florets surrounding numerous yellow disc florets.
Eucephalus glabratus grows at elevations of NaNm (-2,147,483,648feet) in openings in oak and conifer forests or chaparral of the Klamath Mountains of southwestern Oregon and northwestern California.
NatureServe classifies Eucephalus glabratus as Apparently Secure (G4) globally and Vulnerable (S3) in California. It has no state status rank for Oregon.