Australia's chief of the navy, Vice Adm. Ray Griggs, together with government officials, representatives of main contractor BAE Systems and SEPI -- the Spanish state-owned industrial holding company Sociedad Estatal de Participaciones Industriales -- attended the event at Navantia's Ferrol shipyard in Spain.
Construction of the Adelaide started with a steel-cutting ceremony in February 2010 followed by the keel laying a year later, Navantia said.
"This early launch provides additional time, until early 2014, to complete the outfitting and testing of the ship, when the hull will be transported to Australia for completion and delivery by BAE Systems Australia in Williamstown," a statement from Navantia said.
The Adelaide is the second of two landing helicopter dock ships being constructed under a deal signed in Melbourne in 2007 for delivery in 2014 and 2015.
The ships are designed after Navantia's Juan Carlos I vessel delivered to the Spanish navy last year, Navantia said.
The arrival of the first Canberra Class amphibious ship hull, the Canberra, at BAE's Williamstown dockyard, is expected later this year, Australia's Department of Defense said.
"When the (Canberra) hull arrives in Melbourne, the complex task of marrying the superstructure, hull, combat system and communications system can commence, in preparation for delivery of the first ship to the Australian Defense Force in 2014," the Defense Department statement said.
"The LHDs are the largest ships ever built for the Australian navy and will provide the defense forces with one of the most capable and sophisticated amphibious deployment systems in the world."
The Canberra Class LHDs are bigger than Australia's last aircraft carrier Melbourne, a former British vessel built by Vickers-Armstrongs in Barrow-in-Furness, England, in 1945. She served in the Australian navy from 1955 to 1982.
When completed the 27,500-ton ships will be more than 757 feet long and carry more than 1,100 personnel, 100 armored vehicles, 12 helicopters and have a sophisticated 40-bed hospital.
The Canberra and Melbourne will replace one of the Kanimbla class landing platform amphibious ships built by National Steel and Shipbuilding Company for the U.S. Navy in 1971 and the heavy landing ship Tobruk constructed by Carrington Slipways in Tomago, New South Wales, in 1978.
The launch of the Adelaide comes as Australia's Hobart-class air warfare destroyers received the first two AN/SPY-1D(V) phased radar array systems, Defense Materiel Minister Jason Clare said.
The AN/SPY-1D(V) phased array radar serves as the main sensor for the Aegis weapon system, an integrated naval weapons system originally developed by the Missile and Surface Radar Division of RCA and now produced by Lockheed Martin.