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.

The pouched lamprey, also known as the piharau in the North Island, korokoro, kanakana in the South Island, or wide-mouthed lamprey, is a species in the genus Geotria, which is the only genus in the family Geotriidae. The second species in the genus is the Argentinian lamprey, which was revalidated as a separate species in 2020. The pouched lamprey is native to the southern hemisphere. It spends the early part of its life in fresh water, migrating to the sea as an adult, and returning to fresh water to spawn and die.