Evania appendigaster is a species of wasp in the family Evaniidae, the ensign wasps. Its native range is not known, but it likely originated in Asia. Today it occurs throughout the tropics and subtropics and in many temperate regions. It is a parasitoid wasp known for specializing on cockroaches.

This is one of the larger evania appendigaster, with forewings up to about 7 millimeters long. It is distinguished from other species by the wide separation of the first and second sections of the coxa, the segment of the leg that attaches to the body. It is black in color. 

The abdominal petiole, the constricted stalk that holds the posterior section of the abdomen, or gaster, is attached high on the body. The gaster is laterally compressed and oval to nearly triangular in shape, held in a flaglike fashion and resembling an ensign, a characteristic of the family that inspired the common name ensign wasp.