Markham, a city in the Regional Municipality of York, lies within the Greater Toronto Area of Southern Ontario, Canada. At the 2011 Canadian census it had a population of 301,709. The city is the fourth-largest community within the Greater Toronto Area after Toronto, Mississauga and Brampton. Markham changed its status from town to city on July 1, 2012.

The city gained its name from the first Lieutenant-Governor of Upper Canada, John Graves Simcoe (in office 1791-1796), who named the area after his friend, William Markham, the Archbishop of York from 1776 to 1807. The first European settlement in Markham occurred when William Berczy, a German artist and developer, led a group of approximately sixty-four German families to North America. While they initially planned to settle in New York, disputes over finances and land tenure there would eventually lead to Berczy to negotiate with Simcoe for 64,000 acres (260 km2) in Markham Township in 1794. Through much of Markham's history the community has been described as an agricultural community. A turn towards a more urbanized community within the township began after World War II when the township had begun to feel the effects of urban encroachment from Toronto. The completion of Highway 404 during the mid-1970s further accelerated urban development in Markham.

As of 2013 tertiary industry mainly drives Markham. As of 2010 "business services" employed the largest proportion of workers in Markham - nearly 22% of its labour force. The city also has over 900 technology and life-sciences companies, with IBM as the city's largest employer. A number of multinational companies also have their Canadian headquarters located in Markham, including: Honda Canada, Hyundai, Advanced Micro Devices, American Express, Johnson & Johnson, Apple Inc., Avaya, IBM, Motorola, Oracle, Toshiba, Toyota Financial Services and Honeywell.

Markham covers an area of 212.47 km2 (82.04 sq mi) and Markham's City Centre is at 43-¦53?N 79-¦15?W. It is bounded by 5 municipalities; in the west is Vaughan with the boundary along Yonge Street between Steeles Avenue and Highway 7 and Richmond Hill with the boundary along Highway 7 from Yonge Street to Highway 404 and at Highway 404 from Highway 7 to 19th Avenue and Stouffville Road. In the south, it borders Toronto with the boundary along Steeles Avenue. In the North it borders Whitchurch-Stouffville with the boundary from Highway 404 to York-Durham Line between 19th Avenue and Stouffville Road. In the East it borders Pickering along the York-Durham Line.

Markham is made up of many original 19th century communities (many of which, despite being technically suburban districts today, are still signed with official 'city limits' signs on major roads) and/or each with a distinctive character.