King's Highway 129, commonly referred to as Highway 129, is a provincially maintained highway in the Canadian province of Ontario. Located in the Algoma and Sudbury districts, the highway extends for 221 kilometres (137 mi) from a junction with Highway 17 in Thessalon to the town of Chapleau, just north of Highway 101. The route is isolated and lightly travelled throughout its length; while providing access to several remote settlements, the only sizable communities along the route are the two termini. The highway was established in 1956 along the Chapleau Road. From the early 1960s to mid-1970s, Highway 129 was designated as the Chapleau Route of the Trans-Canada Highway.

Algoma District is a district and census division in Northeastern Ontario in the Canadian province of Ontario.