The Ottawa, Arnprior and Parry Sound Railway, or OA&PS, is a historic railway that operated in central and eastern Ontario, Canada from 1897 until 1959. It was, for a time, the busiest railway route in Canada, carrying both timber and wood products from today's Algonquin Provincial Park areas, as well as up to 40% of the grain traffic from the Canadian west from Depot Harbour at Parry Sound through to the St. Lawrence River valley.