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".
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:
- Afrotropical realm
- Antarctic realm
- Australasian realm
- Indomalayan realm
- Nearctic realm
- Neotropical realm
- Oceanian realm
- Palearctic realm
- East Asia north of the Himalayan system's foothills to the Arctic
- Central Asia – Iranian Plateau and north to the Arctic.
- Western Asia
- Northern Africa
- All pages with titles containing Bioregion
- Ecological classification
- Ecology terminology
- Interim Biogeographic Regionalisation for Australia (IBRA)
- Vilhena, D., Antonelli, A. (2015). proach for identifying and delimiting biogeographical regions. Nature Communications 6, 6848, .
- Ecological Framework of Canada – Levels of Generalization
- Berg, P. and Dasmann, R. (1977). Reinhabiting California. The Ecologist 7 (10): 399–401.
- Miller, K. 1999. What is bioregional planning?. In: R. Crofts, E. Maltby, R. Smith and L. Maclean (eds). Integrated Planning: International Perspectives. Battleby, Scotland 7–9 April 1999: IUCN & Scottish Natural Heritage.
- Burgess, N.D.; D'Amico Hales, J.; Dinerstein, E.; et al. (2004). Terrestrial eco-regions of Africa and Madagascar: A conservation assessment. Washington DC.: Island Press 
- Wikramanayake, Eric; Eric Dinerstein; Colby J. Loucks; et al. (2002). Terrestrial Ecoregions of the Indo-Pacific: a Conservation Assessment. Washington, DC: Island Press
- Ricketts, Taylor H., Eric Dinerstein, David M. Olson, Colby J. Loucks, et al. (1999). Terrestrial Ecoregions of North America: a Conservation Assessment. Island Press, Washington DC., 
- Dinerstein, E., Olson, D. Graham, D.J. et al. (1995). A Conservation Assessment of the Terrestrial Ecoregions of Latin America and the Caribbean. World Bank, Washington DC., .