The 3rd Battalion, Royal Australian Regiment (3 RAR) is the armoured infantry battalion of the Australian Army, based in Kapyong Lines, Townsville as part of the 3rd Brigade (Armoured Amphibious). 3 RAR traces its lineage to 1945 and has seen operational service in Japan, Korea, Malaya, Borneo, South Vietnam, Rifle Company Butterworth, East Timor, the Solomon Islands, Afghanistan, and Iraq.

3 RAR was initially formed on 20 October 1945 from volunteers from the 3rd, 6th, 7th and 11th Australian Divisions, as the 67th Battalion of the 34th Brigade (Australia) on Morotai. The battalion was intended to be part of a wider commitment for occupation duties as part of the British Commonwealth Occupation Force in Japan.

The 67th Battalion arrived in Japan as part of the Australian 34th Brigade in February 1946. As with the rest of the occupation force, the battalion did not encounter any significant resistance or civil unrest. The 67th Battalion was redesignated the 3rd Battalion of the Australian Regiment upon its formation in November 1948. The 'Royal' prefix was appended in March 1949. The Australian force in Japan was gradually downsized, with 3 RAR being the only Australian battalion left in the country at the outbreak of the Korean War.

3 RAR was rapidly committed as Australia's main land force contribution to the United Nations forces in the Korean War. After a period of intensive training and reinforcement in Japan, the battalion arrived in South Korea in late September 1950. The battalion formed part of the 27th Commonwealth Brigade and took part in the United Nations offensive into North Korea and the subsequent retreat into South Korea following the Chinese offensive in the winter of 1950–51. In October 1950, the battalion distinguished itself at Chongju during the UN northward advance to the Yalu River. Commanded by Lieutenant Colonel Charles Green, it attacked and captured a large North Korean defensive line in a combined arms operation with tanks and artillery. Green was later killed in action. It was one of three units to receive the US Presidential Unit Citation after the Battle of Kapyong, that was fought between 22 and 25 April 1951.

In July 1951, Major Archer Denness briefly commanded 3 RAR between the departure of Lieutenant Colonel Bruce Ferguson and the arrival of the new commanding officer, Lieutenant Colonel Frank Hassett. Over the period 3–8 October 1951, 3 RAR fought the Battle of Maryang San, which is widely regarded as one of the Australian Army's greatest accomplishments of the Korean War. 3 RAR remained in Korea until November 1954, sustaining total casualties of 231 men killed. Upon its return to Australia, 3 RAR was based at Ingleburn and Holsworthy Barracks, in New South Wales.

The next major conflict that 3 RAR was involved in was the Malayan Emergency. The Australian Government first committed a battalion in 1955 to assist the British colonial occupation in crushing a pro-independence uprising led by the Malayan Communist Party, and their armed wing the Malayan National Liberation Army (MNLA). However, it was not until October 1957 that 3 RAR arrived in theatre; it then commenced a period of acclimatisation at the FARELF Training Centre Kota Tingi (later to become the Jungle Warfare School). 3 RAR then moved to company base camps at Kuala Kangsar (BHQ), Lasah, Sungei, Siput, Penang and Lintang. The unit was engaged in military operations against the MNLA in northern Malaya. Operations began in November 1957 and as a result many MNLA camps and food dumps were located and destroyed. 3 RAR was credited with killing 14 MNLA soldiers and was responsible for the capture of 32 others. 3 RAR casualties over the two years were two wounded and four non-battle casualties. Upon return to Australia, 3 RAR established itself at Enoggera Barracks, Brisbane. It remained there for four years during which time it carried out routine training and barracks duties and was organised on the Pentropic establishment, with five rifle companies and an enlarged headquarters.

3 RAR also served in Malaysia and Borneo during the Indonesia-Malaysia Confrontation and was involved in a series of highly successful cross-border missions under Operation Claret. During these operations the battalion had four major contacts with Indonesian forces on the Sungei Koemba river, at Kindau and again at Babang between May and July 1965. During these operations the battalion lost three men dead and five wounded. 3 RAR moved into Woodside Barracks, South Australia, officially occupying Kapyong Lines at Woodside, on 14 October 1965.

3 RAR served two tours in South Vietnam, the first from December 1967 with the battalion stationed in Phuoc Tuy province as part of the 1st Australian Task Force. The battalion took part in several operations and was involved in mine clearing, counter mortar and rocket tasks and reconnaissance in force operations. Between December 1967 and March 1968 Whisky Company from the Royal New Zealand Infantry Regiment was attached to 3 RAR as an additional rifle company for various phases of battalion operations. As the ready reaction force at the 1ATF base 'A' Company 3 RAR was responsible for clearing and securing the nearby provincial capital of Bà Rịa during the Tet Offensive of February 1968. The battalion was then committed to Operation Coburg in February and March. During 26–28 May 1968, 3 RAR, while stationed at FSB Balmoral in a battalion defensive position, withstood two determined assaults by regimental sized units of the North Vietnamese People's Army of Vietnam (PAVN) during the Battle of Coral–Balmoral. The battalion also played a role in Operation Toan Thang I in April–May 1968. During its first tour of Vietnam the battalion lost 24 killed and 93 wounded.