Jalmenus eichhorni, the northern hairstreak or northern imperial blue, is a butterfly of the family Lycaenidae. It is endemic to Queensland, Australia, including Cape York.
The wingspan is about 30 mm.
The larvae feed on a various Acacia species, including A. crassicarpa, A. leptocarpa, A. humifusa and A. holosericea.
The caterpillars are attended by the ant species Iridomyrmex gracilis, Iridomyrmex reburrus and Iridomyrmex sanguineus.