Square One Shopping Centre is a shopping mall located in Mississauga, Ontario, Canada. It is one of the largest shopping malls in Canada, with over 1.6 million square feet (150,000 m²) of retail space and more than 360 stores and services. On average, the mall serves over 21 million customers each year.

Square One is located at 100 City Centre Drive in central Mississauga, about 20 minutes from downtown Toronto and 15 minutes from Toronto Pearson International Airport. Square One's location is adjacent to the interchange of Highway 403 and Hurontario Street (Highway 10).

The mall is in very close proximity to the Mississauga Civic Centre and the Mississauga Living Arts Centre, both of which are located right across from the mall. Also located near the mall are residential condominiums, Mississauga's Central Library, a large Chapters bookstore and a 13-screen Cineplex Entertainment theatre featuring IMAX (separate from the theatre located inside the mall). The area near the mall is thus a unique combination of residential, government, and entertainment and retail-related commercial areas.

Located within the mall grounds is the main terminal of the Mississauga Transit bus network, which was opened in 1997, and a Peel Regional Police station, which was opened in 2002.

Each year, between June and October, one of the mall parking lots hosts a large farmers' market. The market is open on Fridays and Sundays. For the 2006 season, the market was moved from its previous location at the far end of the Wal-Mart parking lot to a new location, the parking lot located between The Bay and the Mississauga Civic Centre. For the 2007 season, the market was moved once again, this time to a larger location at the northwest parking lot of the mall, near Zellers.

Square One is currently owned and managed by the OMERS Realty Management Corporation through the Oxford Properties Group.