Whitby (2003 population 92,000) is a town located on Lake Ontario, east of Toronto, in Durham Region, Ontario, Canada.

The Town of Whitby was incorporated in 1855, three years after it was chosen as the seat of government for the new County of Ontario. Although settlement dates back to 1800, it was not until 1836 that a downtown business centre was established by Whitby's founder Peter Perry.

Whitby's chief asset was its fine natural harbour on Lake Ontario, from which grain from the farmland to the north was first shipped in 1833. In the 1840s a road was built from Whitby Harbour to Lake Simcoe and Georgian Bay to bring trade through the harbour to and from the rich hinterland to the north. In the 1870s a railway was constructed to Port Perry and Lindsay from Whitby Harbour.

Whitby is also the site of Trafalgar Castle School, a private girls' school founded in 1874. The building, constructed as an Elizabethan-style castle in 1859-62 as a private residence for the Sheriff of Ontario County, is a significant architectural landmark and Whitby's only Provincial historic site marked with a plaque. The school celebrated its 125th anniversary in 1999.

During the Second World War, Whitby was the location of Camp X, a secret spy training facility on the shore of Lake Ontario, established by Sir William Stephenson, the "Man Called Intrepid". Although the buildings have since been demolished, a monument was unveiled on the site of Camp X in 1984 by Ontario's Lieutenant-Governor John Black Aird.

Today, Whitby is the seat of government in Durham Region, and the regional government is the town's largest employer. Also located in the town is the Whitby Mental Health Centre, a large psychiatric hospital.

Several manufacturing businesses are located in Whitby. It is considered part of the Greater Toronto Area even though it belongs to the Oshawa Census Metropolitan Area.

According to Brian Winter, Archivist, Whitby Township (now the Town of Whitby) was named after the seaport town of Whitby, Yorkshire, England. When the township was originally surveyed in 1792, the Surveyor, from the northern part of England, named the townships east of Toronto after towns on England's North-East Coast: York, Scarborough, Pickering, Whitby and Darlington. The name "Whitby" is Danish, dating from about 867 A.D. when the Danes invaded Britain. It is a contraction of "Whitteby," meaning "White Village." The allusion may be to the white lighthouse on the pier at Whitby, Yorkshire, and also at Whitby, Ontario.

North: Scugog
West: Ajax Whitby East: Oshawa
South: Lake Ontario