The Choctaw Nation (Choctaw: Chahta Okla) is a Native American territory covering about 6,952,960 acres (28,138 km²; 10,864 sq mi), occupying portions of southeastern Oklahoma in the United States. The Choctaw Nation is the third-largest federally recognized tribe in the United States and the second-largest Indian reservation in area after the Navajo. As of 2011, the tribe has 223,279 enrolled members, of whom 84,670 live within the state of Oklahoma and 41,616 live within the Choctaw Nation's jurisdiction. A total of 233,126 people live within these boundaries, with its tribal jurisdictional area comprising 10.5 counties in the state, with the seat of government being located in Durant, Oklahoma. It shares borders with the reservations of the Chickasaw, Muscogee, and Cherokee, as well as the U.S. states of Texas and Arkansas. By area, the Choctaw Nation is larger than eight U.S. states.

The chief of the Choctaw Nation is Gary Batton, who took office on April 29, 2014, after the retirement of Gregory E. Pyle. The Choctaw Nation Headquarters, which houses the office of the Chief, is located in Durant. Durant is also the seat of the tribe's judicial department, housed in the Choctaw Nation Judicial Center, near the Headquarters. The tribal legislature meets at the Council House, across the street from the historic Choctaw Capitol Building, in Tuskahoma. The Capitol Building has been adapted for use as the Choctaw Nation Museum. The largest city in the nation had long been McAlester but was recently surpassed by Durant at the 2020 United States census.

The Choctaw Nation is one of three federally recognized Choctaw tribes; the others are the sizable Mississippi Band of Choctaw Indians, with 10,000 members and territory in several communities, and the Jena Band of Choctaw Indians in Louisiana, with a few hundred members. The latter two bands are descendants of Choctaw who resisted the forced relocation to Indian Territory. The Mississippi Choctaw preserved much of their culture in small communities and reorganized as a tribal government in 1945 under new laws after the Indian Reorganization Act of 1934.

Those Choctaw who removed to the Indian Territory, a process that went on into the early 20th century, are federally recognized as the Choctaw Nation of Oklahoma. The removals became known as the "Trail of Tears."

The original territory has expanded and shrunk several times since the 19th century.