- Kingdom: Animalia
- Phylum: Annelida
- Class: Polychaeta
- Subclass: Errantia
- Order: Phyllodocida
- Family: Nereididae
- Scientific name: Nereis pelagica
- Norwegian: fjæreorm
The slender ragworm Nereis pelagica is 6-21 cm long and has 30-100 segments with thin hairs (chaetae) on each segment. The legs, parapods, are positioned closer together than for instance the legs of Hediste diversicolor. A clearly visible blood vessel runs along the back. On the head there are two antennae, two large appendages or palps, and four pairs of tentacles. The most characteristic features are the two appendages or palps, on on each side of the head. These are very large and longer than the antennae. The color is usually golden or bronze, sometimes with a green tint.
It lives in the tidal zone, or just below, under rocks or buried in sand or muddy substrate.
It is found in both the Atlantic and Pacific Oceans, on both hemispheres. It is also registered in the Mediterranean.