King's Highway 11, commonly referred to as Highway 11, is a provincially-maintained highway in the Canadian province of Ontario. At 1,784.9 kilometres (1,109.1 mi), it is the second-longest highway in the province, after Highway 17. Highway 11 begins at Highway 400 in Barrie and arches through northern Ontario to the Ontario–Minnesota border at Rainy River via Thunder Bay; the road continues as Minnesota State Highway 72 across the Baudette–Rainy River International Bridge. North and west of North Bay (as well as for a short distance through Orillia), Highway 11 forms part of the Trans-Canada Highway and is part of MOM's Way between Thunder Bay and Rainy River.
The original section of Highway 11 along Yonge Street was colloquially known as "Main Street Ontario" and was one of the first roads in what would later become Ontario. It was devised as an overland military route between York (Toronto) and Penetanguishene. Yonge Street serves as the east–west divide throughout York Region and Toronto.
Highway 11 became a provincial highway in 1920 when the network was formed, although many of the roads that make up the route were constructed before the highway was designated. At the time, it only extended between Toronto and north of Orillia. In 1937, the route was extended to Hearst, northwest of Timmins. The route was extended to Nipigon by 1943. In 1965, Highway 11 was extended to Rainy River, bringing it to its maximum length of 1,882.2 kilometres (1,169.5 mi). The southernmost leg, an 86-kilometre (53 mi) section (including the Bradford–Barrie extension) through Barrie and south to Lake Ontario in Toronto, also known as Yonge Street, was decommissioned as a provincial highway in 1996 and 1997.
From the late 1940s through the 1960s, numerous bypasses of towns along the route were built, including Orillia, Washago, Gravenhurst, Bracebridge, Huntsville, Emsdale, Powassan, Callander, North Bay, Cobalt, Haileybury, New Liskeard and Thunder Bay. Beginning in the 1960s, the highway was four-laned between Barrie and North Bay in stages. Four laning was completed between Barrie and Gravenhurst in the 1960s, between Gravenhurst and Huntsville in the 1970s, and from North Bay south to Callander in the 1980s. The remaining two lane section between Huntsville and Callander was four laned through the 1990s and 2000s, and was completed in 2012. A section concurrent with Highway 17 east of Thunder Bay was rebuilt as a divided highway in the early 2010s and work continues. The two-lane Nipigon River Bridge was replaced with a twin-span bridge that opened in 2018, following a structural failure in 2016.