Achomawi are the northerly nine bands of the Pit River tribe of Palaihnihan Native Americans who live in what is now northeastern California in the United States. These 5 autonomous bands of the Pit River Indians historically spoke slightly different dialects of one common language, and the other two bands spoke dialects of a related language, called Atsugewi. The name "Achomawi" means river people and properly applies to the band which historically inhabited the Fall River Valley and the Pit River from the south end of Big Valley Mountains, westerly to Pit River Falls. The nine bands of Achumawi lived on both sides of the Pit River from its origin at Goose Lake to Montgomery Creek, and the two bands of Atsugewi lived south of the Pit River on creeks tributary to it in the Hat Creek valley and Dixie Valley.

The Pit River Tribe is a federally recognized tribe of eleven bands of indigenous peoples of California. They primarily live along the Pit River in the northeast corner of California. Their name also is spelled as "Pitt River" in some historical records.