The highway is a 20.0-kilometre (12.4 mi) north–south route in Nipissing District which follows the historic Madawaska Colonization Road.

Highway 523 begins at the boundary between the Hastings County and Nipissing District, east of Algonquin Provincial Park.

It passes through a sparsely populated region dotted with lakes and muskeg, generally remaining straight, though curving sporadically to avoid the many obstacles presented by the Canadian Shield.

It turns back to the north and later approaches the northwestern tip of Bark Lake, on the opposite shore as Bell Bay Provincial Park.

[2] The following table lists the major junctions along Highway 523, as noted by the Ministry of Transportation of Ontario.