The Middle Harbour Syphon is a heritage-listed sewerage syphon located at Monash Crescent (East Side), Clontarf, Northern Beaches Council, New South Wales, Australia. It was designed by E. M. de Burgh, an engineer in the NSW Public Works Department and was built from 1922 to 1925 by the Department. The sewerage syphon is also known as the Middle Harbour Syphon NSOOS and The Spit Syphon. The property is owned by Sydney Water, an agency of the Government of New South Wales. The property was added to the New South Wales State Heritage Register on 15 November 2002.