A neotype of Elasmopus rapax Costa, 1853 is designated based on material from the Fusaro Coastal Lagoon, Central Tyrrhenian Sea, Italy. The species is confirmed as an invasive species in Australian ports. Populations of E. rapax are identified from seven port, harbour, and marina locations around the south-eastern, southern, and south-western coasts. Museum collections indicate that this species has been present in Australia since at least 1884. It is not currently known from tropical Australia.
Keywords: Amphipoda, Maeridae, Elasmopus rapax, neotype, Australia, taxonomy, invasive species