Opasatika is a township in the Canadian province of Ontario, located in the Cochrane District on the Opasatika River, a tributary of the Missinaibi River. Its name is of First Nation origin, meaning "river lined with poplars".The main communities in the township are Opasatika and Lowther, both located along Highway 11 between Mattice and Harty. The ghost town of Reesor Siding, site of the 1963 Reesor Siding incident, is at the western edge of the township.