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 are referred to by different names depending on the Native American dialect spoken.