, the Rosner's hairstreak, is a butterfly of the family . It is found in western North America in British Columbia. and Washington state. Subspecies is known as Barry's hairstreak.
The wingspan is .
The larvae of subspecies M. r. rosneri feed on western red cedar (Thuja plicata), while the larvae of subspecies M. r. plicataria feed on Rocky Mountain juniper (Juniperus scopulorum).
Both and are often treated as subspecies of . is a synonym of .