Commencement Bay is the body of water on which Tacoma, Washington is located. A line drawn from Point Defiance in the west to Browns Point in the east serves to mark the generally accepted division between the bay and the open sound. Part of Washington's inland bay Puget Sound, it has become home to one of the most active commercial ports in the world.

The Puyallup River is the main freshwater stream emptying into the bay. Others include Ruston Creek , Mason Creek , Asarco Creek , Puget Creek , Hylebos Creek , and Wapato Creek .