Hexarthrius parryi can reach a length of about 40–90 millimetres (1.6–3.5 in) in males, of about 40–54 millimetres (1.6–2.1 in) in females (length from the tip of the jaw to wing tip). Some individuals of the Sumatra subspecies (Hexarthrius parryi paradoxus) can reach a length of about 97 millimetres (3.8 in). Body is moderately elongate, not very shining, the basic color is black. Males have long jaws directed downward from the base, with bifurcated tips and a large yellow or bright orange patch occupying the posterior three-quarters of each elytron. The pronolum is short. The lateral angle of the prothorax is very sharp. The head is very broad, quite uneven and rugosely punctured. The mandibles are strongly curved, densely granular, with a sharp tooth directed upwards and another one directed downwards. The front tibia is finely serrated and the middle tibia has a strong lateral spine. The forewing shows a pair of brown spots.