Colorado ( (listen), other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains. Colorado is the eighth most extensive and 21st most populous U.S.

state. The 2020 United States census enumerated the population of Colorado at 5,773,714, an increase of 14.80% since the 2010 census.The region has been inhabited by Native Americans and their ancestors for at least 13,500 years and possibly much longer. The eastern edge of the Rocky Mountains was a major migration route for early peoples who spread throughout the Americas.

"Coloradocode: spa promoted to code: es " is the Spanish adjective meaning "red", the color of the Fountain Formation outcroppings found up and down the Front Range of the Rocky Mountains. The Territory of Colorado was organized on February 28, 1861, and on August 1, 1876, U.S. President Ulysses S. Grant signed Proclamation 230 admitting Colorado to the Union as the 38th state.

Colorado is nicknamed the "Centennial State" because it became a state one century (and four weeks) after the signing of the United States Declaration of Independence. Colorado is bordered by Wyoming to the north, Nebraska to the northeast, Kansas to the east, Oklahoma to the southeast, New Mexico to the south, and Utah to the west, and touches Arizona to the southwest at the Four Corners.

Colorado is noted for its vivid landscape of mountains, forests, high plains, mesas, canyons, plateaus, rivers, and desert lands. Colorado is one of the Mountain states, and is a part of the western, and is often considered to be part of the southwestern, United States. Denver is the capital and most populous city.

Residents of the state are known as Coloradans, although the antiquated "Coloradoan" is occasionally used. Major parts of the economy include government and defense, mining, agriculture, tourism, and increasingly other kinds of manufacturing. With increasing temperatures and decreasing water availability, Colorado's agriculture, forestry, and tourism economies are expected to be heavily affected by climate change.The state is one of the most educated, developed, and wealthiest, ranking 3rd in percentage of population 25 and over with a bachelor's degree and 8th in percentage of population 25 and over with an advanced degree, 9th on the American Human Development Index, and 8th in per capita income and 9th in median household income.