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 others being Pasco and Richland). The population was 73,917 at the 2010 census. The Census Bureau estimates the city's population at 84,347 as of July 1, 2019.
The discovery of Kennewick Man along the banks of the Columbia River provides evidence of Native Americans' settlement of the area for at least 9,000 years. American settlers began moving into the region in the late 19th century as transportation infrastructure was built to connect Kennewick to other settlements along the Columbia River. The construction of the Hanford Site at Richland accelerated the city's growth in the 1940s as workers from around the country came to participate in the Manhattan Project. While Hanford and Pacific Northwest National Laboratory continue to be major sources of employment, the city's economy has diversified over time and now hosts offices for Amazon and Lamb Weston.
Native Americans populated the area around modern-day Kennewick for millennia before being discovered and settled by European descendants. These inhabitants consisted of people from the Umatilla, Wanapum, Nez Perce, and Yakama tribes. Kennewick's low elevation helped to moderate winter temperatures.