The Kiamichi River is a river in southeastern Oklahoma, United States of America. A tributary of the Red River of the South, its headwaters rise on Pine Mountain in the Ouachita Mountains near the Arkansas border. From its source in Polk County, Arkansas, it flows approximately 177 miles (285 km) to its confluence with the Red River at Hugo, Oklahoma.

The Kiamichi Mountains are a mountain range in southeastern Oklahoma. A subrange within the larger Ouachita Mountains that extend from Oklahoma to western Arkansas, the Kiamichi Mountains sit within Le Flore, Pushmataha and McCurtain counties near the towns of Poteau, Albion and Smithville. The foothills of the Kiamichi Mountains sit within Haskell County, Northern Latimer County and Northern Pittsburg County. Its peaks, which line up south of the Kiamichi River, reach 2,500 feet in elevation. The range was the namesake of Kiamichi Country, the official tourism designation for southeastern Oklahoma, until the designation was changed to Choctaw Country.