The town was first incorporated in 1941 when a Defence Industries Limited shell plant was constructed and a townsite grew around the plant. The town was named Ajax after the British light cruiser HMS Ajax. Streets in the town are named after the ship's crew. Although the plant closed when the war ended in 1945, the town survived. Today, Ajax is a suburb of Toronto and is part of the Greater Toronto Area.
| North: Pickering | |||||
| West: Pickering | Ajax | East: Whitby | |||
| South: Lake Ontario |