Markham is now classed as a City in the Regional Municipality of York, located in the Greater Toronto Area of Southern Ontario, Canada. Markham is the fastest growing municipality in Canada, having grown by 70% since the 1991 Census.

Within the Greater Toronto Area, Markham is the fourth-most populous municipality after Toronto, Mississauga, and Brampton. Markham is known for being the Canadian head offices of multinational high-tech companies such as Sony, Avaya, IBM, Motorola, Toshiba, Lucent, Sun Microsystems (now part of Oracle), Apple, AMEX and ATI (now part of AMD).