The Arctic lamprey (Lethenteron camtschaticum), also known as the Japanese river lamprey or Japanese lampern (Petromyzon japonicus Martens 1868, Lampetra fluviatilis japonica (Martens 1868), Lampetra japonica (Martens 1868), Lethenteron japonicum (Martens 1868) ), is a species of lamprey, a jawless fish in the order Petromyzontiformes. It inhabits coastal freshwater habitat types in the Arctic. Some populations are anadromous, spending part of their lives in the ocean. It is the most common and widespread lamprey in the Arctic region.