Nephasoma rimicola is a marine invertebrate belonging to the phylum Sipuncula, the peanut worms.

Near its tip, the introvert has many hook-like spines arranged in six to ten rings, and the mouth is surrounded by well-formed tentacles; there are eight of these in juveniles but more develop as the worm grows, with sixteen being present in most adults and twenty in the largest individuals.

The rings of hooked spines and the well-developed tentacles help to distinguish this species from the usually much smaller Nephasoma minutum which occupies similar habitats.

It has been found in northern Spain and in several shallow water locations around the British Isles, including west of the Isle of Wight, the estuary of the River Exe in north Devon and Milford Haven in south Pembrokeshire where it inhabits crevices in the rock.

The gut is long and J-shaped, with the anus on the dorsal surface of the front end of the trunk.