Cap-Saint-Jacques Nature Park (French: Parc-nature du Cap-Saint-Jacques) is a large nature park in the Pierrefonds-Roxboro borough of Montreal, Quebec, Canada. It is located in the West Island at the junction of the Lake of Two Mountains and the Rivière des Prairies. Situated on a peninsula, three quarters of the park is bordered by water. At 330 ha (820 acres), it is the largest park in Montreal. The land for the park was purchased by the City of Montreal on 15 February 1980 from the Congregation des Soeurs des Saints Noms de Jesus et de Marie.