The Middle Head Fortifications is a heritage-listed former defence establishment and military fortifications and now public space located at Middle Head Road, Middle Head, Mosman in the Mosman Council local government area of New South Wales, Australia. It is also known as the Middle Head Military Fortifications or The Old Fort. The fortifications consist of the Outer Middle Head Battery located at the end of Old Fort Road, the Inner Middle Head Battery located at the end of Governors Road, and the Obelisk batteries reached by a path from the corner of Middle Head Road and Chowder Bay Road. The fortifications at Middle Head formed part of Sydney Harbour's defences. The property is owned by the Department of Planning and Environment. It was added to the New South Wales State Heritage Register on 2 April 1999.

The Sydney Heads are a series of headlands that form the 2 km (1.2 mi) wide entrance to Sydney Harbour in Sydney, New South Wales, Australia. North Head and Quarantine Head are to the north; South Head and Dunbar Head are to the south; and Middle Head, Georges Head, and Chowder Head are to the west and within the harbour. The Heads are contained within the Sydney Harbour National Park.