The Western Hemisphere or occidental hemisphere is a geographical term for the half of the Earth that lies west of the Prime Meridian (which crosses Greenwich, London, United Kingdom) and east of the Antimeridian, the other half being called the Eastern Hemisphere, or "oriental hemisphere".
In this sense, the Western Hemisphere consists of the Americas, the western portions of Europe and Africa, the extreme eastern tip of Russia, numerous territories in Oceania, and a portion of Antarctica, while excluding some of the Aleutian Islands to the southwest of the Alaskan mainland.
The term is often used in political rhetoric to refer to only North and South America (or the New World) and adjacent islands; however, the Western Hemisphere technically includes all of the aforementioned territories.
In an effort to define the Western Hemisphere as the parts of the world which are not part of the Old World, there also exist projections which use the 20th meridian west and the diametrically opposed 160th meridian east to define the hemisphere. This projection excludes the European and African mainlands and a small portion of northeast Greenland, but includes more of eastern Russia and Oceania (e.g., New Zealand).
The population of the geographical Western Hemisphere exceeds 1 billion.
Countries in both hemispheres
Below is a list of the countries which are in both the Western and Eastern hemispheres on the IERS Reference Meridian, in order from north to south:
- United Kingdom
- Denmark (due to Greenland and the Faroe Islands; mainland Denmark lies entirely in the eastern hemisphere).
- Norway (due to Jan Mayen; mainland Norway lies entirely in the eastern hemisphere).
- Netherlands (The Dutch Caribbean islands lie entirely within the western hemisphere while the European Netherlands lies entirely in the eastern hemisphere).
- Burkina Faso
Below is a list of the countries which are in both the Western and Eastern hemispheres along the 180th meridian, in order from north to south:
- Russian Federation
- United States of America (United States islands)
- Wallis and Futuna (France)
Countries in the Western Hemisphere but not in the Americas
The following nations lie outside the Americas yet are in part or entirely within the Western Hemisphere.
- American Samoa (United States of America)
- Burkina Faso
- Cape Verde
- Cook Islands (New Zealand)
- Faroe Islands (Denmark)
- France (Metropolitan)
- Greenland (Denmark) (note: geographically a part of North America, but politically a part of Europe)
- Ivory Coast
- Niue (New Zealand)
- Sierra Leone
- Tokelau (New Zealand)
- United Kingdom
- Oxford Dictionary of English (2nd ed.), London, UK: Oxford University Press, 2006, p. 2001
- "Western Hemisphere", Merriam Webster's Online Dictionary (based on Collegiate vol., 11th ed.), Springfield, MA: Merriam-Webster, 2006
- Olson, Judy M (1997), "Projecting the hemisphere", in Robinson, Arthur H; Snyder, John P, Matching the map projection to the need, Bethesda, MD: Cartography and Geographic Information Society, American Congress on Surveying and Mapping.
- "Western Hemisphere", Merriam-Webster's Geographical Dictionary (3rd ed.), Springfield, MA: Merriam-Webster, 2001, p. 1294.
- "Informe científico que estudia el Aconcagua, el Coloso de América mide 6960,8 metros" [Scientific Report on Aconcagua, the Colossus of America measures 6960,8m] (in Spanish). Universidad Nacional de Cuyo. 2012. Retrieved September 3, 2012.