Megadolomedes australianus is a species of spider endemic to Australia in the family Dolomedidae.

It was first described by Ludwig Carl Christian Koch in 1865.

[2] Females have a total body length of around 31.9 mm (1.26 in).

[3] Where their distribution overlaps with the closely related Megadolomedes trux, they can be distinguished by examination of the palpal tibia in males and the epigyne in females.

[citation needed] M. australianus is known only from New South Wales, from the Nepean River to Wollongong.