Chelan County is a county in the U.S. state of Washington. As of the 2020 census, its population was 79,074. The county seat and largest city is Wenatchee. The county was created out of Okanogan and Kittitas Counties on March 13, 1899. It derives its name from a Chelan Indian word meaning "deep water," likely a reference to 55-mile (89 km)-long Lake Chelan, which reaches a maximum depth of 1,486 feet (453 m).

Wenatchee is the county seat and most populous city of Chelan County, Washington, United States. The population within the city limits in 2010 was 31,925, and has increased to 35,508 as of 2020. Located in the north-central part of the state, at the confluence of the Columbia and Wenatchee rivers near the eastern foothills of the Cascade Range, Wenatchee lies on the western side of the Columbia River, across from the city of East Wenatchee. The Columbia River forms the boundary between Chelan and Douglas County. Wenatchee is the principal city of the Wenatchee–East Wenatchee, Washington Metropolitan Statistical Area, which encompasses all of Chelan and Douglas counties. However, the "Wenatchee Valley Area" generally refers to the land between Rocky Reach and Rock Island Dam on both banks of the Columbia, which includes East Wenatchee, Rock Island, and Malaga, as well as the surrounding towns of Monitor and Cashmere to the west of Wenatchee.