Elminius modestus) is a species of barnacle in the family Elminiidae, native to Australia, Tasmania and New Zealand, but now spread to Britain and the north west coasts of Europe.

It was believed to have arrived on the hulls of ships, or possibly the larval stages travelled in bilge water.

It is found on the upper middle shore and is tolerant of low salinity levels where fresh water enters the sea.

It has feathery appendages which beat rhythmically to draw plankton and other organic particles into the shell for consumption.

[8] It is also a threat to native species because it reaches maturity in its first season and can produce several broods of larvae per year.