Western Hemisphere: The half that lies west of the prime meridian and east of the 180th meridian. This hemisphere includes North and South America, the eastern Pacific Ocean, the Caribbean Sea, and the majority of the Atlantic Ocean.

The Western Hemisphere consists of the Americas, excluding some of the Aleutian Islands to the southwest of the Alaskan mainland; the westernmost portion of Europe, both mainland and islands; the westernmost portion of Africa, both mainland and islands; the extreme eastern tip of the Russian mainland and islands (North Asia); numerous territories in Oceania; and a large portion of Antarctica.