A prairie is an area of land of low topographic relief that principally supports grasses and herbs, with few trees, and is generally of a mesic (moderate or temperate) climate. Most of the Great Plains, most of the states of Ohio, Indiana, Illinois and Iowa, and much of Missouri and Minnesota is considered prairie. French explorers called these areas "prairie", from the French word for "meadow". Almost all of this area has been converted into farmland in the last two hundred years. Sometimes in the USA a distinction is made between the short-grass vegetation of the High Plains west of the 100th meridian and the long-grass vegetation to the east. When that distiction is made, it is common to limit the word "prairie" to the long-grass area.

Prairie grasses.

In Canada, the term "prairie provinces" or "the prairies" refers to the provinces of Alberta, Saskatchewan, and Manitoba. See also Canadian prairies.

Fire is an important part of prairie ecology; natural and human induced fires were common in historic prairie areas. Grazing by animals such as the American Bison and Prairie dogs also helped maintain the original prairie ecology. Small areas of prairies also exist in eastern North America, and it is possible that these were created by Native Americans by periodic burning. One such area was along the southeastern shore of Lake Erie in what is now Pennsylvania and New York; another was between Seneca Lake and Cayuga Lake in present New York.

Prairies are considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type. Other temperate grasslands regions include the Pampas of Argentina, and the steppes of Russia and Ukraine.

Significant preserved areas of prairie include:

• Bong Recreational Area, in Kenosha County, Wisconsin
• Nine-Mile Prairie, Nebraska
• Konza Prairie, Manhattan, Kansas
• Niel Smith Wildlife Refuge, Iowa