Kennewick is a city in Benton County in the U.S. state of Washington. It is located along the southwest bank of the Columbia River, just southeast of the confluence of the Columbia and Yakima rivers and across from the confluence of the Columbia and Snake rivers. It is the most populous of the three cities collectively referred to as the Tri-Cities. The population was 84,488 as of 2021."US Census Information as of 2021".