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."
Kathlamet people also speak English. 