Whitby (2006 population 111,184) is a town in Ontario, Canada. Whitby is located in Southern Ontario east of Toronto on the north shore of Lake Ontario, and is home to the headquarters of Durham Region

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 and settlement through the harbour to and from the rich hinterland to the north. The Town of Whitby was chosen as the seat of government for the newly formed County of Ontario in 1852, and incorporated in 1855. In the 1870s a railway, the "Port Whitby and Port Perry Railway," was constructed from Whitby harbour to Port Perry, and later extended to Lindsay as the "Whitby, Port Perry and Lindsay Railway."

In 1968, the Town of Whitby and Township of Whitby amalgamated to form the current municipality. Municipal boundaries were not changed during the 1974 formation of Durham Region and remain to this day.

Today, Whitby is the seat of government in Durham Region. It is commonly considered part of the Greater Toronto Area, although for census purposes it belongs to the greater Oshawa Metropolitan Area. They are both in the eastern part of the Golden Horseshoe region.