A bioregion is an ecologically and geographically defined area that is smaller than a biogeographic realm, but larger than an ecoregion or an ecosystem, in the World Wide Fund for Nature classification scheme. There is also an attempt to use the term in a rank-less generalist sense, similar to the terms "biogeographic area" or "biogeographic unit".
It may be conceptually similar to an ecoprovince.
It is also differently used in the environmentalist context, being coined by Berg and Dasmann (1977).
Main article: Global 200
The World Wide Fund for Nature (WWF) scheme divides some of the biogeographic realms into bioregions, defined as "geographic clusters of ecoregions that may span several habitat types, but have strong biogeographic affinities, particularly at taxonomic levels higher than the species level (genus, family)." The WWF bioregions are as follows: