Trithuria australis is a species of aquatic plant in the family Hydatellaceae endemic to Western Australia.

[1] Trithuria australis is an annual,[2] submerged aquatic plant.

Both female and male reproductive units are present on the same plant.

[2] The reproductive units are sessile or exhibit very short peduncles.

[1][2] The type specimen was collected by L. Diels in Hamersley River, Western Australia in October 1901.