The 21st Construction Regiment (21 CR) is a construction engineer regiment of the Australian Army Reserve. Part of the 5th Brigade, the regiment was formed in 1950 and is based in New South Wales where it provides support to the 2nd Division. The regiment has recently contributed personnel to a number of operations including the Regional Assistance Mission to the Solomon Islands, Operation Slipper and Operation Astute. It also regularly supports the Army Aboriginal Community Assistance Program and provides assistance to the Australian community in times of natural disaster.