Ionactis stenomeres, the Rocky Mountain aster, is a rare North American species in the family Asteraceae. It occurs in the Province of British Columbia in western Canada and also in the northwestern United States (Washington, Idaho, Montana).
Ionactis stenomeres is a small perennial up to tall, with a woody underground caudex. The plant usually produces only one flower head, each with 7-21 blue or lavender ray flowers surrounding yellow disc flowers.