The Western Hemisphere is a geographical term for the half of Earth which lies west of the prime meridian (which crosses Greenwich, London, United Kingdom) and east of the antimeridian. The other half is called the Eastern Hemisphere.
The Western Hemisphere consists of the Americas, the western portions of Europe and Africa, the extreme eastern tip of Siberia (Russia), numerous territories in Oceania, and a portion of Antarctica, while excluding some of the Aleutian Islands to the southwest of the Alaskan mainland.
In an attempt 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.
The center of the Western Hemisphere is located 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 .
Below is a list of the sovereign states which are in both the Western and Eastern Hemispheres on the IERS Reference Meridian, in order from north to south:
Below is a list of the sovereign states which are in both the Western and Eastern Hemispheres along the 180th meridian, in order from north to south. With the exception of the United States (Wake Island), all of them are located on just one side of the International Date Line, which is curved around them.
One sovereign state has territory on both hemispheres, but neither the prime meridian nor the 180th meridian passes through its territory:
The following countries and territories lie outside the Americas yet are entirely/mostly or partially within the Western Hemisphere: