We describe a new species of drepanidine bird from a fossil found in a lava tube cave on the island of Hawaii. The bill of the new species combines a long, scimitar-like maxillary rostrum with a much shorter mandibular rostrum, giving the bird a most unusual appearance. The general bill form is shared with members of the drepanidine genus Hemignathus, to which the new species is referred, although it is quite distinct from other species of Hemignathus in aspects of its bill morphology and in its much larger body size. The scimitar-like maxilla appears to be adapted to probing in cracks or crevices and possibly to moving loose material, such as leaf detritus, to obtain invertebrate prey. The species became extinct <3,000 years ago.