Middle Head Fortifications, Colonial military fortifications in Middle Head, Australia.

Middle Head Fortifications consist of the Outer and Inner Middle Head Batteries and the Obelisk batteries, built mainly between 1870 and 1911, with the first fort on the site dating from 1801. The batteries were designed by colonial architect James Barnet to fire on ships entering through Sydney Heads. Visitors see low grey concrete gun emplacements, a pillbox with a narrow horizontal opening, and a tall weathered column with an empty recessed panel.

The British colonial government began constructing these defenses in 1801 to protect Sydney from maritime attacks. Later upgrades between 1870 and 1911 modernized the defensive capabilities against emerging threats.

The name "The Old Fort" is still used locally for the Middle Head batteries. Below ground, rooms were used for "Code of Conduct" courses, training some of Australia's first troops sent to Vietnam to withstand torture and interrogation by simulating prisoner of war conditions. The site also appeared in the 1974 film Stone.

The site is split into three parts: the Outer Battery at the end of Old Fort Road, the Inner Battery at the end of Governors Road, and the Obelisk batteries via a path from Middle Head Road and Chowder Bay Road. Paths connect the batteries, tunnels and underground rooms; some passages are unlit and uneven underfoot.

The complex features a disappearing gun emplacement, an innovative 19th-century defense device that lowered into the ground when activated. This technology represented advanced engineering for its era and demonstrated the skill of colonial military architects.