Platynereis is a genus of marine annelid worms that belongs to the Nereididae, a family of errant polychaete worms.

[1][2] The species Platynereis dumerilii is used in development biology to study development (embryogenesis), in particular because their embryos are largely transparent, and thus easy to follow.

[3] Apical organs such as this one are photosensitive which is a key component in their formation.

They also have a common ancestor with cnidarians and bilaterians.

This annelid-related article is a stub.