Oklahoma () is a state in the South Central region of the United States, bordered by the state of Texas on the south and west, Kansas on the north, Missouri on the northeast, Arkansas on the east, New Mexico on the west, and Colorado on the northwest. Partially in the western extreme of the Upland South, it is the 20th-most extensive and the 28th-most populous of the 50 United States. Its residents are known as Oklahomans (or colloquially “Okies”), and its capital and largest city is Oklahoma City.

The state’s name is derived from the Choctaw words okla and humma, meaning “red people”. It is also known informally by its nickname, “The Sooner State”, in reference to the non-Native settlers who staked their claims on land before the official opening date of lands in the western Oklahoma Territory or before the Indian Appropriations Act of 1889, which increased European-American settlement in the eastern Indian Territory. Oklahoma Territory and Indian Territory were merged into the State of Oklahoma when it became the 46th state to enter the union on November 16, 1907.

With ancient mountain ranges, prairie, mesas, and eastern forests, most of Oklahoma lies in the Great Plains, Cross Timbers, and the U.S. Interior Highlands, all regions prone to severe weather. Oklahoma is on a confluence of three major American cultural regions and historically served as a route for cattle drives, a destination for Southern settlers, and a government-sanctioned territory for Native Americans. Twenty-five Native American languages are spoken in Oklahoma.

A major producer of natural gas, oil, and agricultural products, Oklahoma relies on an economic base of aviation, energy, telecommunications, and biotechnology.Oklahoma City and Tulsa serve as Oklahoma’s primary economic anchors, with nearly two-thirds of Oklahomans living within their metropolitan statistical areas. These cities, collectively known as the Oklahoma Metropolitan Corridor, are included in the Texas Triangle megaregion.