The Stillaguamish people are a Southern Coast Salish people Indigenous to the Stillaguamish River valley in northwestern Washington State in the United States, near the city of Arlington, Washington. The Stillaguamish speak Northern Lushootseed, a Coast Salish language. Although usage of the language has declined, there are ongoing revitalization efforts by the Stillaguamish Tribe.

Lushootseed, formerly known as Puget Salish, Puget Sound Salish, or Skagit-Nisqually, is a Central Coast Salish language of the Salishan language family. Lushootseed is the general name for the dialect continuum composed of two main dialects, Northern Lushootseed and Southern Lushootseed, which are further separated into smaller sub-dialects.