Lepeophtheirus pectoralis is a species of parasitic copepod from the northeast Atlantic Ocean, and the type species of the genus Lepeophtheirus. It is a parasite of flatfish, with the European flounder (Platichthys flesus), the plaice (Pleuronectes platessa), and the dab (Limanda limanda) as the most frequent hosts. It feeds on the mucus, skin, and blood of the fish, with egg-producing females infecting the pectoral and pelvic fins of the host, while immature individuals and males are found on the rest of the body.