Portal:Military history of Australia/Selected anniversaries/June/June 21
- 1911 – The first 42 cadets are inducted into the Royal Military College Duntroon, consisting of 32 Australians and 10 New Zealanders. The college was officially opened six days later.
- 1951 – Korean War: 3rd Battalion, Royal Australian Regiment is awarded the Presidential Unit Citation, for "extraordinary heroism and outstanding performance" during the Battle of Kapyong.