The frilled shark or frill shark (Chlamydoselachus anguineus) is a primitive shark, the sole living member of the Chlamydoselachidae in the order Hexanchiformes. It is very different from the other hexanchiforms, and has been recently proposed to be given its own order Chlamydoselachiformes. Additional extinct types are known from fossil teeth.
Superficially the frilled shark resembles a dark brown or gray eel, but the six gill slits identify it as a shark. The tissue of the gill slits protudes somewhat, thus inspiring the name. Its dorsal fin is small, anal fin large, and the caudal fin is highly asymmetric, the ventral part almost unnoticeable. Its teeth are small tricuspid, and very sharp. It has been recorded at up to 2 meters in length.
Reproduction is not well understood, but like many other sharks they bear live young, with litter sizes of 2 to 12. It has been suggested that the gestation period is about 3.5 years, which would give the frilled shark the longest gestation of any vertebrate, considerably exceeding the elephant's period of 22 months.
Frilled sharks appear regularly in the catches from bottom trawling, and when caught are used as food or for fishmeal.