Mississauga is a Canadian city in the province of Ontario. Situated on the northwestern shore of Lake Ontario in the Regional Municipality of Peel, it borders Toronto (Etobicoke) to the east, Brampton to the north, Milton to the northwest, and Oakville to the southwest. With a population of 717,961 as of 2021, Mississauga is the seventh-most populous municipality in Canada, third-most in Ontario, and second-most in the Greater Toronto Area (GTA) after Toronto itself. However, for the first time in its history, the city's population declined according to the 2021 census, from a 2016 population of 721,599 to 717,961, a 0.5 per cent decrease.

The growth of Mississauga was initially attributed to its proximity to Toronto. However, during the latter half of the 20th century, the city attracted a diverse and multicultural population. Over time, it built up a thriving, transit-oriented central business district of its own; the Mississauga City Centre. Malton, a neighbourhood of the city located in its northeast end, is home to Toronto Pearson International Airport, Canada's busiest airport, as well as the headquarters of many Canadian and multinational corporations. Mississauga is not a traditional city, but is instead an amalgamation of three former villages, two townships, and a number of rural hamlets (a general pattern common to several suburban GTA cities) that were significant population centres, with none being clearly dominant, prior to the city's incorporation that later coalesced into a single urban area.

Indigenous people have lived in the area for thousands of years and Mississauga is situated on the traditional territory of the Wendat, Haudenosaunee and Anishinaabeg people, including the namesake Mississaugas. Most of present-day Mississauga was founded in 1805 as Toronto Township within York County, and became part of Peel County when new counties were formed by splitting off parts of the original county in 1851. Mississauga itself was established in 1968 as a town, and was reincorporated as a city in 1974, when Peel was restructured into a regional municipality.

The name Mississauga comes from the Anishinaabe word Misi-zaagiing, meaning '[those at the] Great River-mouth'.

Other forms such as Sauga and, in reference to the city's residents, Saugans, and Mississaugans, are also commonly used.

A single site in Mississauga with Hi-Lo projectile points was registered in the Ontario Ministry of Culture database of archaeological sites. Lake Ontario was much smaller at this time, and sites from this period may be 500 m into the lake.

According to Smith, there was a growing population at this time. There are 23 known Archaic sites in Mississauga, mostly in the Credit River and Cooksville Creek drainage systems. People would congregate at rapids and the mouths of these rivers to catch fish during spawning runs. They would harvest nuts and wild rice at the wetland margins in the late summer. During late Archaic times, there were large cemeteries.

"The accelerating upward population increase continued," with 23 known sites from this period. Pottery first appears during this period in the style of the Point Peninsula complex, and near the end of the Woodland period, the first semi-permanent villages appear. Artifacts show that these people engaged in long-distance trade, likely as part of the Hopewell tradition.