The air-land-sea amphibious vessel, along with sister ship HMAS Canberra, enhances the strength of the navy to defend the nation.
The 230m long and 27,000t assault ships were designed to guide in littoral waters and ports. They can deploy an embarked force of around 1,000 personnel.
Both the LHDs feature an eight bed critical care unit, as well as resuscitation, pathology, radiology, x-ray, pharmacy, and dental facilities.
HMAS Adelaide commanding officer Captain Paul Mandziy said: "This is a proud and momentous occasion that symbolises the culmination of the amount of time, support and hard work that has gone into realising this capability.
"As the second of class, lessons learnt from HMAS Canberra, our sister ship, has sped up our introduction into service, but a lot of effort and energy was still required from my ship’s company to get us prepared for today."
The ship will be used in humanitarian assistance and disaster relief, security, and stability operations across the Indo-Pacific region.
It can be landed ashore by new landing craft, helicopters, or a combination of both.
The navy is planning to add three Hobart Class Destroyers to its fleet in 2016.
Image: The Australian White Ensign being raised during the commissioning of HMAS Adelaide. Photo: courtesy of the Royal Australian Navy.