Lepeophtheirus pectoralis is a species of parasitic copepod. It is a parasite of flatfish, the most frequent hosts being the European flounder, Platichthys flesus, the plaice, Pleuronectes platessa and the dab, Limanda limanda. It feeds on the mucus, skin and blood of the fish, with oviferous females being found in the pectoral and pelvic fins of the host, while immature individuals and males are found in the rest of the body.