Ajax (/ˈeɪdʒæks/; 2011 population 109,600) is a town in the Durham Region of Southern Ontario, Canada, located in the eastern part of the Greater Toronto Area.

The town is named for HMS Ajax, a Royal Navy cruiser that served in World War II. It is approximately 25 kilometres (16 mi) east of Toronto on the shores of Lake Ontario and is bordered by the City of Pickering to the west and north, and the Town of Whitby to the east.

Before the Second World War, the territory in which Ajax is situated was a rural part of the township of Pickering. The town itself was first established in 1941 when a Defence Industries Limited (D.I.L.) shell plant was constructed and a townsite grew around the plant. By 1945 the plant had filled 40 million shells; employed over 9,000 people at peak production; boasted of its own water and sewage treatment plants; a school population of over 600; 50 km (31 mi) of railroad and 50 km (31 mi) of roads. The entire D.I.L. plant site included some 12 km2 (5 sq mi). People came from all over Canada to work at D.I.L.

The burgeoning community received its name in honour of the first significant British naval victory of the war. From December 13 to December 19, 1939, a flotilla of British warships — HMS Ajax, HMS Exeter and HMS Achilles — commanded by Commodore Henry Harwood — engaged and routed the powerful German pocket battleship Admiral Graf Spee at the Battle of the River Plate, near the Uruguayan port of Montevideo in South America. Ajax was chosen as the name of this war-born community.

After the war, the University of Toronto leased much of the D.I.L. plant to house the flood of newly discharged soldiers who had enrolled as engineering students. War machines were moved out and the buildings were converted to classrooms and laboratories. By 1949, the last year of the University of Toronto, Ajax Division, some 7,000 engineering students had received their basic training there.

Following the departure of the University of Toronto, the town’s growth was largely due to the vision of George W. Finley of Canada Mortgage and Housing Corporation, and Ajax became a planned modern community using the wartime base for its post-war foundation.

From 1941 to 1950, Ajax had no local municipal government of its own. In 1950, as a result of a petition, the community became the Corporation of the Improvement District of Ajax with three trustees appointed by the Lieutenant-Governor in Council. By 1953, the desire for full and active participation by its citizens in an elected council and school board was strong. The Ajax Citizens’ Association, formed by many civic-minded persons, presented a brief to the Ontario Municipal Board urging that the Improvement District of Ajax become the Corporation of the Town of Ajax. The Municipal Board approved this step, and on December 13, 1954, the people elected the first Town Council and the first Public School Board.

On June 22, 1973, the Ontario Legislature enacted Bill 162 to amalgamate the Town of Ajax and the Village of Pickering and annex certain portions of the Township of Pickering to the Town of Ajax, as part of the creation of the new Durham Region; this also included the remote lakeside Town of Pickering Beach. The Region and Town both officially came into being on January 1, 1974.

Today, Ajax is commonly considered part of the Greater Toronto Area, in the eastern part of the Golden Horseshoe region.

As is true for most suburban areas in the Greater Toronto Area, Ajax has grown considerably since the 1980s. What was once a small town mostly surrounded by agricultural areas has increasingly become a bedroom community to Toronto and its environs. Many residents commute to work in Toronto or other municipalities in Durham Region.

The following is a summary of major changes in the past several decades:

Recent rapid low density population growth. Only one greenfield area of the Town remains, located in the north western corner of the town. As the town becomes increasingly built-out, the town is attempting to increase intensity of development, particularly in the downtown area near Harwood Avenue north of Bayly. However, development in Ajax still principally consists of single-family detached houses on separate lots, and so the fundamental nature of the town seems fixed for the near future. Recently, these areas have expanded to north Ajax. the reason is the large amount of land that can be capitalized on for housing investment. Although these projects have been going on for many years, until recently these homes have been constructed and citizens have now been residing in these homes. this has ultimately contributed to the population increase in Ajax.

The town’s very auto dependent urban form, as well as that of its neighbour municipalities, has resulted in steady increases in traffic congestion with few realistic alternatives to automobile travel. There are long-term plans to widen regional roads and Highway 401, extend Highway 407, but this essentially represents status quo development. Increases in Durham Region Transit service, ongoing efforts to improve cycling and walking conditions, and the above noted intensification initiatives may alleviate this to some degree.
Increasing multiculturalism, with many young ethnic professionals moving into the newer northern parts of Ajax. These northern parts of Ajax namely consist of Rossland Road and Taunton Road. Given the large number of homes being built in the area for the last few years, this newer complex is home to plazas and sports recreational facilities. Summer camps and soccer clubs often find these recreational areas worthwhile given the new field and its aesthetic majesty. Parks are also built on this area and are mostly located in or nearby recreational facilities.

Ajax Council and a private developer entered into an agreement in 2012 for the purchase and sale of 9 acres (3.6 ha) of vacant town-owned land at the corner of Bayly Street and Harwood Avenue. Called “Pat Bayly Square”, it will provide residential, retail and office space, as well as a civic square and civic facility.

In 2013, Ajax Council and a private developer unveiled a $118.7 million residential, office, and retail development planned for downtown Ajax called “Grand Harwood Place”. The Town of Ajax stated that “site plan approval is expected by spring 2015”.