Z Special Unit (/zɛd/) was a joint Allied special forces unit formed during the Second World War to operate behind Japanese lines in South East Asia. Predominantly Australian, Z Special Unit was a specialist reconnaissance and sabotage unit that included British, Dutch, New Zealand, Timorese and Indonesian members, predominantly operating on Borneo and the islands of the former Dutch East Indies.
The unit carried out a total of 81 covert operations in the South West Pacific theatre, with parties inserted by parachute or submarine to provide intelligence and conduct guerrilla warfare. The best known of these missions were Operation Jaywick and Operation Rimau, both of which involved raids on Japanese shipping in Singapore Harbour; the latter of which resulted in the deaths of 23 commandos either in action or by execution after capture.
Although the unit was disbanded after the war, many of the training techniques and operational procedures employed were later used during the formation of other Australian Army special forces units and they remain a model for guerrilla operations to this day.