Yakima County is a county located in the U.S. state of Washington. As of the 2010 census, its population was 243,231. The county seat and largest city is Yakima. The county was formed out of Ferguson County on January 21, 1865 and is named for Yakama tribe of Native Americans. Ferguson County, no longer in existence, had been created from Walla Walla County on January 23, 1863.
Yakima County comprises the Yakima, WA Metropolitan Statistical Area.
The Yakama Indian Reservation, the 15th largest reservation in America, covers 1,573 mi², comprising 36% of the county's total area. Its population was 31,799 in 2000, and its largest city is Toppenish.