The 9th Division was a division of the Australian Army that served during World War II. It was the fourth division raised for the Second Australian Imperial Force (2nd AIF). The distinctions of the division include it being:

in front line combat longer, cumulatively, than any other Australian division;

one of the Australian military's most decorated formations;

the only 2nd AIF division formed in the United Kingdom, from infantry brigades and support units formed in Australia;

praised by both Allied and Axis generals, including Bernard Montgomery and Erwin Rommel, as well as non-Australian military historians, and;

like the 6th and 7th Divisions, being one of only a few Allied army units to serve in both the Mediterranean and Pacific theatres.During 1940, the component units of the 9th Division were sent to the UK to defend it against a possible German invasion. After serving during 1941–1942 in the North African campaign, at the Siege of Tobruk and both the First and Second Battles of El Alamein, the 9th Division returned to Australia. In 1943–1944, it served in the New Guinea campaign and, during 1945, in the Borneo campaign. It was disbanded, following the end of the war, in early 1946.