Gynacantha kirbyi is a species of dragonfly in the family Aeshnidae, known as the slender duskhawker. It is found in northern Queensland, Australia, the Maluku Islands, Tanimbar and New Guinea.
Gynacantha kirbyi is a large, dull-coloured dragonfly with a strongly constricted waist in its abdomen at segment 3. Wings of the female have a brown colouring near their base. It is a crepuscular insect and flies at dawn and dusk.