The Kathlamet people are a tribe of Native American people with a historic homeland along the Columbia River in what is today southwestern Washington state. The Kathlamet people originally spoke the Kathlamet language, a dialect of the Chinookan language. They were also called "Guasámas, or Guithlamethl, by the Clackamas", and "Kwillu'chini, by the Chinook."
The tribe that lived in the southwestern Washington state spoke many languages, including the Kathlamet and recently moved along the Columbia River.