Planning to upgrade the navy's amphibious fleet began in 2000, based on Australian experiences leading the International Force for East Timor peacekeeping operation.

In 2004, French company Direction des Constructions Navales (DCN) and Spanish company Navantia were invited to tender proposals, with DCN offering the Mistral-class amphibious assault ship and Navantia proposing the "Buque de Proyección Estratégica" design (later commissioned as Juan Carlos I).

The ships are home-ported at Fleet Base East in Sydney (which has prompted complaints from nearby residents about machinery noise, exhaust fumes, and blocked views) and will regularly operate out of Townsville, the location of Lavarack Barracks, home of the Australian Army's 3rd Brigade.

[7] Alternately, a member of the Australian Naval Institute opined that the ships should be named Gallipoli and Guadalcanal; the first reflecting the landings at Gallipoli, one of the first amphibious operations of the modern era, the second recognising the amphibious campaign to recapture Guadalcanal and the efforts of the United States Navy and United States Marine Corps in aiding Australia during World War II.

[12] On 20 June 2007, Minister for Defence Brendan Nelson announced that the A$3 billion contract to build the Canberra class had been awarded to Navantia and Tenix.

[13][14] Although an unproven design, the Spanish offer was closer to the RAN's requested requirements, and there were benefits from ordering the Canberras and the new Hobart-class air warfare destroyers from the same company.

[12] At around the time the decision to purchase the ships was made, many defence analysts advocated for acquiring a larger number of smaller vessels on the grounds that this would be better suited to conditions in Australia's region.

[19] Keeping the maximum draught low was an important factor during design, allowing the ships to operate in littoral waters and small harbours.

[19] The Canberras have the same physical dimensions as Juan Carlos I, but differ in the design of the island superstructure and the internal layout, in order to meet Australian conditions and requirements.

[4] Propulsion is provided by two Siemens Navantia 11-megawatt (15,000 hp) azimuth thrusters, each with an onboard electric motor, driving two 4.5-metre (15 ft) diameter propellers.

[19] HMAS Canberra was reported to have completed a major maintenance period in the Captain Cook Graving Dock at Garden Island during which the propulsion pods were replaced including new 4 bladed propellers.

At the time of reporting (March 2021) Canberra was preparing for sea trials and plans were being made for HMAS Adelaide to undergo similar maintenance.

[4] The sensor suite includes a Sea Giraffe 3D surveillance radar, and a Vampir NG infrared search and track system.

[25] Each ship has a 69.3-by-16.8-metre (227 by 55 ft) well deck, that houses up to four LHD Landing Craft (LLC, the RAN designation for the LCM-1E), which can be launched and recovered in conditions up to Sea State 4.

[19] Two aircraft lifts (one large one centre-aft, and a smaller one to starboard and in front of the island superstructure) connect the flight and hangar decks.

[37][38] This assessment found that the cost of modifying the ships to operate jets would be very high, and the idea was rejected before the completion of the White Paper.

[39] Opponents to operating F-35s from the Canberra class state that embarking enough aircraft to be an effective force would require abandoning their capability as amphibious warfare vessels, operating as an aircraft carrier would make the ships higher profile targets and need greater escorting forces, existing fuel and ordnance storage would not be able to sustain fixed-wing operations, structural modifications were needed to reinforce and heat-treat the flight deck to withstand F-35B vertical thrust, and the F-35B project itself has been the most expensive and most problematic of the three Joint Strike Fighter variants.

[33][40][41] Supporters counter that providing fixed-wing air support close to amphibious operations maximises aircraft capability, other nations are already working on solutions to structural and thrust problems for other Harrier-era ships, and the presence of a ski-jump makes the vessels already more suitable for STOVL operations than equivalent amphibious ships with flat flight decks.

[4][14][43] The Canberras were built up to the flight deck, launched, then transported by Dockwise's heavy lift ship, Blue Marlin, to Williamstown, Victoria, where the installation of the island superstructure and the internal fitout of the hull was completed by BAE Systems Australia (which acquired Tenix in mid-2008).

[4][43] Fitting out of the ship progressed at a faster rate than expected, which has brought the predicted commissioning date back to late 2015.

[63] Robertson was commanding officer of the carrier Melbourne at the time of the Melbourne–Voyager collision in 1964, and was widely seen to be a scapegoat after the first Royal Commission found him to be at fault.

[68] Defence also spent A$5.3 million to lease and develop a dedicated staging area for equipment and personnel within the Port of Townsville precinct.