Two separate iterations of Highway 516 have existed in Ontario over the years. The first existed between 1956 and 1972 in Muskoka. The current Highway 516 in northwestern Ontario was designated in 1983.
Muskoka The original iteration of Highway 516 was designated alongside many other secondary highways by the DHO on May 9, 1956. The highway began in Windermere and travelled east along the southern shore of Three Mile Lake, passing through the village of
Ufford along the way. The route briefly turned north
concurrent with
Highway 532 near
Raymond before resuming eastward. It passed through the village of Utterson before ending at Highway 11 (now Greer Road) between Utterson and Port Sydney. The highway was extended east to Port Sydney in 1960, bringing it to its peak length of . Following the formation of the
District Municipality of Muskoka on January 1, 1971, most of the secondary highways within the new district were transferred to it and redesignated as part of its
district road system. Highway 516 west of Highway 532 became part of Muskoka District Road 4. Highway 532 was rerouted along the portion of Highway 516 east to Highway 11 and would become Highway 141. The remaining segment east of Highway 11 became Muskoka District Road 10. By 1973, Highway 516 had been decommissioned entirely.
Northwestern Ontario During the mid-1970s, a new road was constructed between Sioux Lookout and Highway 599 north of Savant Lake to provide access to the pulpwood and iron ore resources in the area. It was given the unsigned designation of Highway 708, but was better known as the Marchington Lake Road. Although it was completed in 1977, it was not assumed as a provincial highway until 1982 or 1983. Highway 516 first appeared in 1982–83 official Ontario road map as an unpaved route. It is shown as a paved highway on the 1984 official road map. Highway 516 has remain unchanged since then. == Major intersections ==