Austrophlebia costalis, the southern giant darner, is a species of dragonfly in the family Aeshnidae endemic to eastern Australia.
Austrophlebia costalis is an enormous dark dragonfly with strong yellow markings on its body and a brown band along the leading edge of its wings. It inhabits streams and may be found on logs in shady areas.
This species is believed to be one of the fastest flying odonates, with an old reference claiming to have clocked one at nearly but no modern confirmation.