A new species of scorpionfish, Scorpaena gasta, is described on the basis of five specimens collected from the warm temperate central coast of Western Australia, eastern Indian Ocean, at depths of 3–7 m. Scorpaena gasta is most similar to a Western Australian species, S. sumptuosa. The two species are distinguished from other Indo-Pacific species of Scorpaena by the following combination of characters: lateral surface of maxilla with a distinct longitudinal ridge; relatively thick skin with numerous small sensory pores covering nearly the entire predorsal area to near the first pored lateral-line scale; anteroventral surface of lower jaw with one or two pairs of slender tentacles in ventral view. Scorpaena gasta and S. sumptuosa are separated by four meristic, several morphometric, and color features. Scorpaena gasta is a small species (smallest mature female 67.4 mm SL; largest known specimen 83.6 mm SL), whereas S. sumptuosa is a relatively large species, attaining at least 241 mm SL.