The Royal South Australia Regiment is a reserve regiment

Regiment

A regiment is a major tactical military unit, composed of variable numbers of batteries, squadrons or battalions, commanded by a colonel or lieutenant colonel...

 of the Australian Army

Australian Army

The Australian Army is Australia's military land force. It is part of the Australian Defence Force along with the Royal Australian Navy and the Royal Australian Air Force. While the Chief of Defence commands the Australian Defence Force , the Army is commanded by the Chief of Army...

 consisting of a single battalion, the 10th/27th Battalion, part of the 9th Brigade

Australian 9th Brigade

The 9th Brigade is an Reserve formation of the Australian Army headquartered at Keswick Barracks in Keswick, South Australia, with elements located in Tasmania, South Australia, New South Wales and the Northern Territory.-History:...

. It was raised on 1 July 1960, as The South Australia Regiment.
The Regiment traces much of its history to early volunteer and citizen militia units from pre-federation Australia. The history of the units that formed the current Regiment are dealt with individually on those pages.
On the 1st of July 1960 the South Australia Regiment was formed by the amalgamation of three infantry battalions in South Australia:

• The 10th Infantry Battalion (The Adelaide Rifles)
• 43rd/48th Infantry Battalion (The Hindmarsh Regiment)
• 27th Infantry Battalion (The South Australia Scottish Regiment)
  27th Battalion (Australia)
  The 27th Battalion was an infantry battalion of the Australian Army. It was initially raised in 1915 as part of the First Australian Imperial Force for service during World War I. During the conflict, the battalion saw action briefly at Gallipoli before later fighting on the Western Front between...
  
  .

These three battalions were formed into 5 Companies:

• A Company (The South East Company) (from the SA Scottish Regt)
• B Company (The River Company) (from the SA Scottish Regt)
• C Company (The Mid North Company) (from the Hindmarsh Regt)
• D Company (The Adelaide Company) (from the Adelaide Rifles)
• E Company (The Port Adelaide Company) (from the Adelaide Rifles)

Later in 1960, The Regiment was renamed 1st Battalion Royal South Australia Regiment, bringing it in line with the other State and National regiments.