The Americas are the region of the Western hemisphere that consists of the continents of North America and South America with their associated islands and regions. The Americas cover 8.3% of the Earth's total surface area (28.4% of its land area) and contain about 14% of the human population (about 900 million people). The Americas may alternatively be referred to as America; however, "America" may be ambiguous, as it is commonly used to refer to the United States of America.

South America broke off from the west of the supercontinent Gondwanaland around 135 million years ago (Ma), forming its own continent. Starting around 15 Ma, the collision of the Caribbean Plate and the Pacific Plate resulted in a series of volcanoes along the border that created a number of islands. The gaps in the archipelago of Central America filled in with material eroded off North America and South America, plus new land created by continued volcanism. By 3 Ma, the continents of North America and South America were linked by the Isthmus of Panama, thereby forming the single landmass of the Americas. South America is made up of 11 countries. The biggest is Brazil.

 

The northernmost point of the Americas is Kaffeklubben Island, which is the northernmost point of land on Earth. The southernmost point is the islands of Southern Thule, although they are sometimes considered part of Antarctica. The easternmost point is Nordostrundingen. The westernmost point is Attu Island.

 

The western geography of the Americas is dominated by the American cordillera, with the Andes running along the west coast of South America and the Rocky Mountains and other Pacific Coast Ranges running the western side of North America. The 2300 km long Appalachian Mountains run along the east coast of North America from Alabama to Newfoundland. North of the Appalachians, the Arctic Cordillera runs along the eastern coast of Canada.

Between its coastal mountain ranges, North America has vast flat areas. The Interior Plains spread over much of the continent with low relief. The Canadian Shield covers almost 5 million km² of North America and is generally quite flat. Similarly, the north-east of South America is covered by the flat Amazon Basin. The Brazilian Highlands on the east coast are fairly smooth but show some variations in landform, while further south the Gran Chaco and Pampas are broad lowlands.