An introduced, neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its native distributional range, which has arrived there by human activity, either deliberate or accidental.

Some introduced species are damaging to the ecosystem they are introduced into, others have no negative effect and can in fact be beneficial: to humans-as an alternative to pesticides in agriculture for example-and to Ecosystems, as in New Zealand where introduced species of flora from North America have been shown to increase Biodiversity and Bioproductivity. A list of introduced species is given in a separate article. Introduced species and their effects on natural environments is a controversial subject and one that has gained much scrutiny by scientists, governments, farmers and others.