Eau Claire () is a city in Chippewa and Eau Claire counties in the west-central part of the U.S. state of Wisconsin. Located almost entirely in Eau Claire County, for which it is the county seat, the city had a population of 65,883 at the 2010 census, making it the state's ninth-largest city. Eau Claire is the principal city of the Eau Claire, Wisconsin Metropolitan Statistical Area, which is a part of the Eau Claire-Menomonie Combined Statistical Area.
Eau Claire took its name from Eau Claire County. "Eau Claire" is the singular form of the original French name, "Eaux Claires", meaning "Clear Waters", for the Eau Claire River. According to local legend, the river was so named because early French explorers journeying down the rain-muddied Chippewa River, came upon the confluence with the Eau Claire River, and excitedly exclaimed "Voici l'eau claire!" ("Here is the clear water!") Now used as the city motto, this appears on the city seal.
The area of Eau Claire was first visited by Europeans in the late 17th century. It had been occupied for thousands of years before European fur traders began settling there for trade with local Native American tribes.
The First Treaty of Prairie du Chien signed in 1825 established the Chippewa River "half a day's march below the falls" as the boundary marker between the Sioux and Chippewa, and the "Clear Water River, a branch of the Chippewa" as the boundary between the Chippewa and Winnebago.
The first permanent European-American settlers arrived in 1845, and the city was officially incorporated in 1872. The extensive timber was harvested and logging was the major industry during this time; many sawmills were built as part of the lumber industry.