Oastler Lake Provincial Park is a provincial park in the municipality of Seguin, Parry Sound District in Central Ontario, Canada. The nearest town, just to the northwest, is Parry Sound. Oastler Lake is a recreation-class park, 32 hectares in size, on the shore of Oastler Lake where the Boyne River flows in from Otter Lake. It is located along a former alignment of Highway 69 which now has the street name Oastler Park Drive.