The sea lamprey is a parasitic lamprey native to the Northern Hemisphere. It is sometimes referred to as the "vampire fish". In its original habitats, the sea lamprey coevolved with its hosts, and those hosts evolved a measure of resistance to the sea lampreys.

Lampreys are a group of jawless fish comprising the order Petromyzontiformes. The adult lamprey is characterized by a toothed, funnel-like sucking mouth. The common name "lamprey" is probably derived from Latin lampetra, which may mean "stone licker", though the etymology is uncertain. Lamprey is sometimes seen for the plural form.