The Western Hemisphere is the half of the planet Earth that lies west of the Prime Meridian and east of the 180th meridian. The other half is called the Eastern Hemisphere. In the United States, the term "Western Hemisphere" is often used as a metonym for the Americas, even though geographically, the hemisphere also includes parts of other continents.
Geography
The Western Hemisphere comprises the Americas, except some of the Aleutian Islands to the southwest of the Alaskan mainland; the westernmost parts of Europe and Africa, both mainland and islands; the extreme eastern tip of the Russian mainland and islands (North Asia); many territories in Oceania; and a large part of Antarctica.
The center of the Western Hemisphere on the surface of the Earth is in the Pacific Ocean, at the intersection of the 90th meridian west and the Equator, among the Galápagos Islands. The nearest land is Genovesa Island at .
The largest country entirely in the Western Hemisphere is Canada at 9,984,670 km2.Political Handbook of the World 2024-2025, p. 292. United States: SAGE Publications, 2025. Fifteen independent countries entirely in the Western Hemisphere have no land borders to other countries: Antigua and Barbuda, the Bahamas, Barbados, Cape Verde, Cuba, Dominica, Grenada, Iceland, Jamaica, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Samoa, Tonga and Trinidad and Tobago. Various other island entities in the Western Hemisphere are semi-independent territories of countries, while the Dominican Republic, Ireland and Haiti are considered divided island countries, due to having land borders. Ten of Africa's 54 independent countries are entirely in the Western Hemisphere: the largest is Mauritania at 1,030,000 km2. Five African countries are partially in the Western Hemisphere. Three of Europe's 44 independent countries are entirely in the Western Hemisphere, while seven are partially in it. Portugal is the only mainland European country entirely in the Western Hemisphere, and Spain has the most mainland European land in the Western Hemisphere. However, a moderate proportion of Spain's population still live in the Eastern Hemisphere, since the major city of Barcelona is part of the small part of Spain east of the prime meridian. While the Polynesian countries of Samoa and Tonga are part of the Western Hemisphere, no countries from the neighboring regions of Melanesia and Micronesia are entirely in the Western Hemisphere.
The highest mountain in the Western Hemisphere is Aconcagua, in the Andes of Argentina, at .
The tallest freestanding structure in the Western Hemisphere is the CN Tower, in Toronto, at . The tallest building in the Western Hemisphere is One World Trade Center, in New York City, at .
Other definitions The inclusion of parts of non-American areas such as Western Europe is controversial among some, since it conflicts with constructs of the Western Hemisphere which correlate it with the New World or the Americas.Mamadouh, Virginie. "Divided we stand: Plural geopolitical visions of the West." Tampere Peace Research Institute, pp. 2-3. 2006. Under the accepted geographical definition, historical events such as The Great Fire of London () are considered to have occurred in the Western Hemisphere, despite not being events associated with the history of the Americas and the New World. Similarly, facts such as Brazil being the last country to abolish slavery in the Western Hemisphere are not technically valid under the geographical definition of the Western Hemisphere, as slavery continued in the Western Hemisphere in non-American areas, with Mauritiana being the last country in the world to abolish slavery in 1981. In an attempt to match the Western Hemisphere more closely with the Americas, some sources use the 20th meridian west and the diametrically opposed 160th meridian east to define the hemisphere.. . This definition excludes all of the European and African mainlands, but still includes some islands associated with these continents, more of eastern Russia and Oceania, and part of Antarctica. It includes all islands of Alaska, but excludes a small portion of northeast Greenland. There is no hemisphere that includes all of the Americas that also excludes all land outside the Americas, regardless of the meridians or points chosen to define it.
Temperature records The majority of Antarctica's lowest recorded temperatures have been recorded in the larger Eastern Hemisphere portion. Outside of Antarctica, the lowest temperature ever recorded in the Western Hemisphere was a −69.6°C (−93.3°F) reading at the Klinck Automatic Weather Station in Greenland on December 22, 1991. This is also the lowest temperature ever recorded in the Northern Hemisphere. Byrd Automatic Weather Station is situated in the Western Hemisphere portion of Antarctica and recorded a −64.4 °C (−83.9 °F) reading on July 18, 1985. The lowest temperature ever recorded in the Eastern Hemisphere and the Southern Hemisphere was a −89.2 °C (−128.6 °F) reading at Antarctica's Vostok Station on July 21, 1983. This is also the lowest temperature ever recorded on earth.
The 56.7°C (134°F) temperature recorded in Death Valley, California on July 10, 1913 is the highest temperature ever recorded in the Northern Hemisphere and Western Hemisphere.Steinacker, R. (2025). The 1913 maximum temperature world record at Death Valley: should we expect a new record in the near future?. Oxford Open Climate Change, 5(1), kgaf015. It is also the highest temperature ever recorded on earth. A 55.0°C (131°F) temperature recorded in Kebili, Tunisia, on July 7, 1931 is the second highest temperature ever recorded on earth, and the highest in the Eastern Hemisphere. However, some weather historians question its accuracy. A 1922 reading of 58 °C (136.4 °F) in El Azizia, Libya, was long cited as the world record before the World Meteorological Organization decertified it in 2012 due to measurement errors.https://www.reuters.com/article/markets/commodities/hot-story-libya-loses-temperature-record-to-death-valley-idUSL5E8KD8S3/ The Southern Hemisphere's highest recorded temperature is tied at 50.7 °C (123.3 °F) between Oodnadatta, South Australia on January 2, 1960 and Onslow, Western Australia on January 13, 2022.
Rivadavia, Argentina recorded South America's highest ever temperature of 48.9°C (120°F) on December 11, 1905. Seymour Island is situated off the coast of Antarctica's Western Hemisphere portion, and recorded a temperature of 20.75 °C (69.35 °F) on February 9, 2020, the highest associated with the Antarctica region.
Human history Morocco has some of the earliest evidence of habitation by modern forms of humans, dating back to 315,000 years ago. Some areas in West Africa like Ivory Coast and Senegal are believed to have had settlements from modern forms of humans dating to 150,000 years ago. Modern humans reached Portugal, Spain and Great Britain roughly 43,000 years ago, with Ireland being reached 10,000 years ago. The Americas were settled by humans roughly 15,000 years ago. Iceland and the Faroe Islands were settled over 1,000 years ago. Samoa and Tonga were settled 3,000 years ago, although other areas in Polynesia like Easter Island and Hawaii were settled under 1,000 years ago. Some areas in the Western Hemisphere were uninhabited by humans before the Age of Discovery, including Ascension Island, Baker Island, Cape Verde, the Cayman Islands, Clipperton Island, Cocos Island, the Desventuradas Islands, the Falkland Islands, Fernando de Noronha, the Galápagos Islands, Howland Island, Jarvis Island, the Juan Fernández Islands, Midway Atoll, the Revillagigedo Islands, Saint Helena, South Georgia and the South Sandwich Islands, Trindade and Martim Vaz and Tristan da Cunha.Macnaughtan, Don. "Mystery Islands of Remote East Polynesia: Bibliography of Prehistoric Settlement on the Pitcairn Islands Group." Island Bibliographies (2014). The part of Antarctica in the Western Hemisphere was also uninhabited before the Age of Discovery.
Environment Fauna In the fauna of the Americas, there are distinct evolutionary lineages that evolved in geographic isolation, particularly during the Cenozoic Era. Among the most distinct native mammals are the xenarthrans, an ancient group that includes anteaters, armadillos and sloths. These animals originated in South America and remain exclusive to the Americas today. Similarly, New World monkeys—such as capuchins, spider monkeys, and howler monkeys, form a distinct primate family that evolved separately from Old World monkeys in Afro-Eurasia. The entire hummingbird family, comprising over 300 species, exists naturally only in the Americas, ranging from Alaska to the southern tip of Chile. New World vultures, including turkey vultures and the Andean and California condors, are evolutionarily distinct from Old World vultures.
Bald eagles, the national symbol of the United States, can on rare occasion be found in the Eastern Hemisphere towards the end of Alaska's Aleutian Islands chain, which stretches across the North Pacific Ocean. While penguins are nearly exclusive to Antarctic-influenced regions of the Southern Hemisphere, they are widely found in both the Eastern and Western Hemisphere. Similarly, polar bears, which are exclusive to Arctic-influenced regions of the Northern Hemisphere, can be found in both the Eastern and Western Hemisphere.Prestrud, Paul, and Ian Sterling. "The International Polar Bear Agreement and the current status of polar bear conservation." Aquatic Mammals 20 (1994): 113-113.
Western chimpanzees only occur in African countries west of the prime meridian, including Guinea, Guinea-Bissau, Ivory Coast, Liberia, Senegal and Sierra Leone, which are entirely west of the prime meridian, and Ghana and Mali, which are mostly west of it. Western chimpanzees have gone extinct in Benin, which is entirely east of the prime meridian, and Togo, which is mostly east of it. However, other chimpanzee species occur throughout the Eastern Hemisphere portion of Africa. Various African animals such as giraffes, gorillas and zebras only occur in its Eastern Hemisphere portion.
Geology The land of the Western Hemisphere encompasses several major tectonic plates, and a number of smaller plates and plate-boundary systems. The continental portions of Canada, the United States, Greenland and much of Mexico are situated mainly on the North American Plate. The Baja California Peninsula and adjacent areas are part of the Pacific Plate system, which is also associated with several Mexican offshore islands. Mexico's Revillagigedo Islands, including Socorro, San Benedicto and Clarion, are situated on the Pacific Plate and form a volcanic archipelago in the eastern Pacific. Clipperton Island, an uninhabited French territory situated 1,080 kilometers off Mexico, is also in the eastern Pacific and lies near the boundary between the Pacific Plate and the Cocos Plate. Its volcanic origin is associated with the broader tectonic and volcanic processes of the region. Most of Central America and the Caribbean occupy the Caribbean Plate or lie along its boundaries with the North American, Cocos and South American plates. Cuba and the Cayman Islands are notable exceptions within the Greater Antilles, as they lie on the North American Plate, whereas Hispaniola, Puerto Rico, Jamaica and the Virgin Islands lie on the Caribbean Plate. The Lesser Antilles form a volcanic arc associated with the eastern boundary of the Caribbean Plate, where Atlantic oceanic lithosphere is subducted beneath the Caribbean region. Most of South America is situated on the South American Plate. Along South America's western margin, the Nazca Plate is being subducted beneath the South American Plate, producing the Peru–Chile Trench, the Andes and one of the world's most active earthquake and volcanic zones. Aside from South America itself, the Falkland Islands are also situated on the South American Plate.