The 6th Cavalry Brigade was a militia or Citizens Military Force (CMF) formation of the Australian Army based in South Australia.

In South Australia in addition to the 6th were elements of the divisional troops such as an artillery battery, engineers, signals, field ambulance and service corps.

Likewise, due to financial stringencies, a number of its units were forced to amalgamate with regiments linking and unlinking in this period.

The bombing of Pearl Harbor in December 1941, the fall of Singapore on 15 February, the bombing of Darwin on 19 February 1942 and occupation of the Philippines and Dutch East Indies, fuelled concerns in Australia that the Japanese would continue their aggressive occupation of South East Asia through to the South Pacific.

It was tasked with forming a district reserve, and defending positions along the Onkaparinga and Stuart Rivers, in South Australia.