A region is an area of land that has common features. A region can be defined by natural or artificial features. Language, government, or religion can define a region, as can forests, wildlife, or climate.

Regions, large or small, are the basic units of geography. The Middle East is considered a political, environmental, and religious region that includes parts of Africa, Asia, and Europe. The region is in a hot, dry climate. Although the styles of government are varied (theocracy in Iran, monarchy in Saudi Arabia), almost all of them have strong ties to religion. The region is where three of the world's major religions were founded: Christianity, Judaism, and Islam.

The Amazon region in South America is the area surrounding the Amazon River, which runs through the northern part of the continent, including Brazil, Bolivia, Ecuador, and Peru. This region is characterized by warm temperatures, heavy rainfall, a large diversity of plant and animal species, and little human impact on the environment.

Geographers also use regions to study prehistoric environments that no longer exist. Due to plate tectonics, or the movement of Earth's crust, geographic regions are constantly being created and destroyed over time. Paleogeography is the study of these ancient environments.

One paleogeographic region is Pangaea, the supercontinent that existed millions of years ago, during the Paleozoic and Mesozoic eras. The continents we know today split apart from the supercontinent of Pangaea.

Regions of the United States

There are many different ways to divide the United States into regions. The Library of Congress lists 16 different U.S. regions.

• Atlantic States: all states that border the Atlantic Ocean, from Maine to Florida
• East: all states east of the Mississippi River
• Middle Atlantic States: Delaware, District of Columbia, Maryland, New Jersey, New York, and Pennsylvania
• Middle West or Midwest: from the Rocky Mountains to the Allegheny Mountains; Illinois, Iowa, Indiana, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin
• New England: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont
• Northeast: east of the Mississippi River, north of the Ohio and Potomac rivers: Connecticut, Delaware, District of Columbia, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Vermont, and Wisconsin
• Northwest: states between Lake Superior and the Pacific Ocean: Idaho, Iowa, Kansas, Minnesota, Missouri, Montana, Nebraska, North Dakota, Oregon, South Dakota, Washington, and Wyoming
• Pacific Northwest: old Oregon country: Idaho, Oregon, Montana, Washington, and Wyoming
• Pacific States: all states that border the Pacific Ocean: Alaska, California, Hawai'i, Oregon, and Washington
• Rocky Mountain: Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Utah, and Wyoming
• South Atlantic: Florida, Georgia, North Carolina, South Carolina, Virginia
• South: states south of the Mason-Dixon Line: Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia
• New Southwest: Arizona, California, Colorado, Nevada, New Mexico, and Utah
• Old Southwest: Arkansas, Kentucky, Louisiana, Missouri, Tennessee, and Texas
• Southwest: Arkansas, Arizona, California, Colorado, Nevada, New Mexico, Texas, and Utah
• West: all states west of the Mississippi River