Eau Claire (/oʊˈklɛər/ ^ⓘ oh-KLAIR; French: [o klɛʁ] lit. 'clear water') is a city in Eau Claire and Chippewa counties in the U.S. state of Wisconsin. It is the county seat of Eau Claire County. It is the seventh-most populous city in Wisconsin, with a population of 69,421 at the 2020 census (estimated at 72,331 in 2024). The Eau Claire metropolitan area, known locally as the Chippewa Valley, has approximately 176,000 residents.

Eau Claire is at the confluence of the Eau Claire and Chippewa rivers on traditional Ojibwe, Dakota, and Ho-Chunk land. The area's first permanent European American settlers arrived in 1845, and Eau Claire was incorporated as a city in 1872. The city's early growth came from its extensive logging and timber industries. After Eau Claire's lumber industry declined in the early 20th century, the city's economy diversified to encompass manufacturing and Eau Claire became an educational center with the opening of the University of Wisconsin–Eau Claire in 1916.

Eau Claire is known regionally for its arts and music scenes and is the hometown of indie folk band Bon Iver, whose lead singer Justin Vernon co-curated the city's annual Eaux Claires Music & Arts Festival. Eau Claire is also a regional commercial and business center and home to the headquarters of home improvement store chain Menards. Eau Claire is the second-fastest growing major city in Wisconsin after Madison, with 5.4% population growth between 2010 and 2020.

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 the contrast: "Voici l'eau claire!" ("Here is the clear water!"). Now the city motto, this appears on the city seal.

The Eau Claire area 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 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. Extensive timber was harvested and logging was the major industry during this time; many sawmills were built as part of the lumber industry. Sawmills and other manufacturing made Eau Claire an industrial city by the late 19th century.

The city was founded near the confluence of the Eau Claire and Chippewa rivers as three separate settlements. The main section of downtown is on the site of the original European-American village, where Stephen McCann, in partnership with J. C. Thomas, put up three buildings in 1845. Although these structures were erected primarily to establish a claim to the land site, the McCann family moved into one of them and became the first permanent settlers.