The Regiment traces much of its history to early volunteer and citizen militia units from pre-federation Australia.

Units were raised, disbanded and perpetuated in a variety of forms that is not easy to show in a simple list.

Often units, depending on their status as volunteer, militia, or regular, were similarly numbered and named, for example the 43rd Infantry Battalion and 2/43 Battalion, AIF in World War II, and often units were split, amalgamated, resplit and reformed, making it almost impossible to create a straight family tree as is often seen for the British Army.

A broad statement is that the Royal South Australia Regiment is preceded by units often known as the 10th (or 78th or Adelaide Rifles), 27th (or SA Scottish or Boothby), 43rd (or 76th or SA Infantry or Hindmarsh), and 48th (or Torrens), and units bearing these designations are now perpetuated in RSAR.

Current structure: As part of the Plan Beersheba Reforms, the 81 mm mortar-equipped 6th/13th Light Battery (formed through an amalgamation of the 16th and 48th Field Batteries) and 3rd Field Squadron were absorbed in the Battalion in 2013 and 2014 respectively in order to provide the Battalion with organic offensive support coordination and indirect firepower, and light engineering support.