The Lane Cove River is a tributary of the Parramatta River and its lower reaches form an arm of Sydney Harbour, Australia. The Lane Cove River rises near Thornleigh and flows generally south for about 15 km. The upper reaches are in a narrow, forested valley eroded into the North Shore Plateau. The middle reaches are impounded by a weir near Fullers Bridge. Sections of the valley form the Lane Cove National Park. The lower reaches of the Lane Cove River are tidal and merge into Sydney Harbour at Greenwich and Hunters Hill. There are significant areas of mangrove trees on the shores.