Diphlebia coerulescens, known as the sapphire rockmaster,[3] is an Australian species of broad winged damselfly.

[3] English-born entomologist, Robin Tillyard described the sapphire rockmaster as a subspecies of the tropical rockmaster, Diphlebia euphaeoides in 1913, before reassessing it as a separate species on the basis of the distinct shape of the male anal appendage, as well as differences in size and colour of the adults.

It can be distinguished from the tropical rockmaster by the larger size of two prominent blue markings at the base (front end) and underside of terga 4 to 6.

The wings are narrower than the tropical rockmaster, but wider than the other members of the genus, and are a smoky brown rather than black.

The upperside of its abdomen is a dark olive-green,[5] with a darker dorsal line prominently running down the midline,[3] which widens into a roughly triangular pattern at the rear end of each segment (tergum).