A tribe of American Indians that formed part of the Illinois nation (see Illinois). In the late 1600s, the Kaskaskia tribe occupied the northeastern portion of Illinois territory in the upper Illinois River valley southwest of Lake Michigan. French explorers Jacques Marquette and Louis Jolliet visited the Grand Village of Kaskaskia (Zimmerman site) on their famous voyage in 1673. The Kaskaskia vacated the Illinois River in 1700 when they moved to the mouth of the Kaskaskia River in southwestern Illinois. They remained in that area until the early 1800s, when they signed treaties ceding their land east of the Mississippi River. Today, their descendants are represented by the Peoria Tribe of Indians of Oklahoma.

Kaskaskia, Illinois, on the Mississippi River, was occupied on July 4, 1778, during the Revolutionary War, by George Rogers Clark, command troops from Virginia. Cahokia, Illinois, and Vincennes, Indiana, soon capitulated, though the Britsh later reoccupied Vincennes before Clark recaptured it on February 23, 1779. Clark's operations strengthened American claims to the areas at the end of the war.

The Kaskaskia were one of the several cognate tribes that made up the Illiniwek Confederation. Their first contact with Europeans reportedly occurred near present-day Green Bay, Wisconsin in 1667 at a Jesuit mission station. The Illiniwek are reported to have asked the French to send a missionary to them in their home country.