Markham is a town in the Regional Municipality of York, located in the Greater Toronto Area of Southern Ontario, Canada. Markham is the largest town in Canada, and one of its fastest growing municipalities, having doubled its population since 1990. The population of Markham according to the Canada 2006 Census is 261,573. Within the Greater Toronto Area, Markham is the fourth-most populous municipality after Toronto, Mississauga, and Brampton. Markham is home to many high-tech companies, and is also home to the Canadian head offices of various high-tech companies such as Avaya, IBM, Motorola, Toshiba, Lucent, Sun Microsystems, Apple, AMEX and ATI, which is now part of AMD.