Geodorcus montivagus is a large flightless species of stag beetle in the family Lucanidae. It is known from only one female specimen found on the Victoria Range in New Zealand. It was found in tussock at above sea level.
The specimen found has a body length, including its mandibles of 21.1mm. It has a black and glossy exoskeleton. The mandibles are short, arched and toothed.
This species has been classified as data deficient under the New Zealand Threat Classification System .[1]