Spongiobranchaea australis is a species of sea angel, a form of sea-slug plankton.

It has a partially transparent body with small "wings" that it uses to swim in its habitat.

Spongiobranchaea australis is found in austral waters near the Antarctic region, in the southern hemisphere.

The species is primarily concentrated near areas in close proximity to Australia and New Zealand.

Regular sexually active males and females vary around 3–5 mm.