Oklahoma ( OHK-lə-HOH-mə; Choctaw: Oklahumma, pronounced [oklahómma]) is a state in the South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northeast, Arkansas to the east, New Mexico to the west, and Colorado to 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 and its capital and largest city is Oklahoma City. The state's name is derived from the Choctaw words okla, 'people' and humma, which translates as 'red'. Oklahoma is also known informally by its nickname, "The Sooner State", in reference to the Sooners, American settlers who staked their claims in formerly American Indian-owned lands until the Indian Appropriations Act of 1889 authorized the Land Rush of 1889 opening the land to settlement.

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 at a confluence of three major American cultural regions. Historically, it served as a government-sanctioned territory for American Indians moved from east of the Mississippi River, a route for cattle drives from Texas and related regions, and a destination for Southern settlers. There are currently 26 Indigenous languages spoken in Oklahoma. According to the 2020 U.S. census, 14.2 percent of Oklahomans identify as American Indians, the highest indigenous population by percentage in any state.

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.