Waukesha (/ˈwɔːkɪʃɔː/ ^ⓘ WAW-ki-shaw) is a city in and the county seat of Waukesha County, Wisconsin, United States. The population was 71,158 at the 2020 census. Located along the Fox River adjacent to the Village of Waukesha, it is the eighth-most populous city in Wisconsin. Waukesha is part of the Milwaukee metropolitan area.

"Waukesha" is thought to be an Anglicization of the Ojibwe word Waagoshag, the plural of fox (waagosh), or the Potawatomi name Wau-tsha. Wau-tsha (sometimes written as Wauk-tsha or Wauke-tsha) was the leader of the local tribe at the time of the first European settlement of the area. This is confirmed by accounts of Increase A. Lapham, an early settler and historian of the region. According to Lapham, the Algonquian word for "fox" was pishtaka. Cutler also told visitors about Wau-tsha, who was described as "tall and athletic, proud in his bearing, dignified and friendly."

The Waukesha area was first settled by European-Americans in 1834, with Morris D. Cutler as its first settler. The founders of Waukesha were settlers from New England, part of a wave of New England farmers who headed west into what was then the wilds of the Northwest Territory during the early 1800s. Most arrived as a result of the completion of the Erie Canal as well as the end of the Black Hawk War. When the first settlers arrived, there was nothing but dense virgin forest and wild prairie. The settlers laid out farms, constructed roads, erected government buildings and established post routes. They brought many of their Yankee values, such as a passion for education, establishing many schools as well as staunch support for abolitionism. They were mostly members of the Congregationalist Church though some were Episcopalian. Due to the second Great Awakening some had converted to Methodism and others had become Baptists before moving to Waukesha County. Like much of Wisconsin, Waukesha would be culturally very continuous with New England culture for most of its early history.

By 1846, the area was incorporated as the town of Prairie Village (soon changed to Prairieville). On February 8, 1847, the town changed its name to "Waukesha". On January 10, 1852, the settled area once known as Prairieville was separated from the town of Waukesha and incorporated as a village; it incorporated as a city in 1896. The first appointed mayor of the newly incorporated city of Waukesha was John Brehm, who served from January to April 1896. Welsh immigrants settling in Waukesha as early as the 1840s, and large numbers arrived in the late 1800s and early 1900s, when they were one of the largest ethnic groups in Waukesha. In the late 1800s a large number of Belgian families arrived in Waukesha as well. Around the same time there was also relatively large amounts of Serbian immigrants settling in Waukesha, many more of which arrived after the Yugoslav Wars much later in the 1990s.

Matthew Laflin, an early pioneer of Chicago, Illinois, provided the capital and enterprise that laid the foundation for Waukesha as a famous Wisconsin watering resort and was the proprietor of the grand resort, the Fountain Spring House. Waukesha was once known for its extremely clean and good-tasting spring water and was called a "spa town." This earned the city the nicknames "Spring City" and "Saratoga of the West."

According to author Kristine Adams Wendt, in 1868, Colonel Richard Dunbar, a sufferer of diabetes, chanced upon the medicinal properties of what he later named the Bethesda Spring while viewing a parcel of land recently purchased by his sister. Testimonials found in a Dunbar brochure of 1873 proclaimed the miraculous benefits. Wendt reports that by 1872, "area newspapers carried accounts of a community ill equipped to handle its new popularity among the suffering multitudes. The semi-weekly Wisconsin (Milwaukee) of July 31, 1872, reported 'that fully 500 visitors are quartered in hotels and scattered in private families here, seeking benefit from the marvelous waters…'"

The "healing waters" were so valued that a controversial attempt was made to build a pipeline between the city and Chicago so that they could be enjoyed by visitors to the 1893 Columbian Exposition. According to Time magazine, "[t]he scheme had been conceived by one Charles Welsh who had been given the springs by his uncle, but after several miles of pipe were laid, it was discovered that the cost was too great." Richard Warren Sears, founder of Sears and Roebuck, may have been attracted to Waukesha by the waters. In failing health, Sears retired from business in 1908 and, according to The New York Times, "spent his time on his great farm near Waukesha." In 1914, Sears died in Waukesha of Bright's disease, leaving an estate estimated at $20 million.

Over the years, the natural springs have been spoiled by pollution and a number have gone dry. Water drawn from an aquifer reached radium levels exceeding federal standards.