Regiment Groot Karoo was an infantry battalion of the South African Army.

The regiment was garrisoned in Craddock, but had sections at Graaf Reinet, Steynsburg, Burgersdorp, Middelburg, Umtata and Aliwal North.

The regiment's first formal training was conducted in East London in 1935 and mainly dealt with the use of the Vickers machinegun.

With South Africa's entry in World War II, the Middellandse Regiment got the opportunity to prove itself.

The regiment was assigned to the 9th Infantry Brigade and finally to the 2nd South African Division.

After 5 October 1941, 2nd South African Division was placed under command of the 8th Army and moved to Bagush.

The regiment was now responsible for anti-aircraft and area defence at the Fuka airfield as well as protecting the railway line and coast between Bagush and Mersa Matruh.

The rational was that the previous name had no real purpose except to distinguish it from other units and just indicated a locality where the regiment originated from.

The new name also brought a change in the unit's insignia, but the merino rams head was retained with it now facing head-on.

The regiment participated in the South African Border War, as part of 82 Mechanised Brigade.