- For other meanings, see Appaloosa (disambiguation).
The Appalousa (also Opelousa) were Native Americans who had occupied the area around Opelousas, Louisiana west of the lower Mississippi River before European contact and encountered in the 18th century. They were associated with the Atakapa and the Chitimacha at various times in their history.
The name Opelousas has been thought to have many meanings, but the one most commonly accepted is "Blackleg", possibly because the tribe painted or stained their legs a dark color. 
Michel De Birotte, who lived in Louisiana from 1690 to 1734, about forty years of which he spent living among the Indians, said the Appalousa lived just west of two small lakes, thought to be Leonard Swamp, east of Opelousas. This was the westernmost channel of the Mississippi River in earlier times. Because of mineral deposits and the great number of leaves covering the bottom, the waters of the lake were black. Appalousa hunting and fishing in the lake found their legs became stained black from the stagnant waters.
Dr. John Sibley reported in a 1805 letter to Thomas Jefferson that the Opelousa speak a language different from all others but also understand Atakapa and French. Their language is completely undocumented.
- Hebert, Rev. Donald J., "Appendix C: Rummaging through old church records of Opelousas", Southwest Louisiana Records, Vol 1B, Complete Revision, 1996. p762.
Goddard, Ives. (2005). "The indigenous languages of the Southeast", Anthropological Linguistics, 47 (1), 1–60.