The largest ship ever built for the Australian Navy has been welcomed into the fleet, with the HMAS Canberra formally commissioned for service.

The commissioning service was held in Sydney with Governor-General Sir Peter Cosgrove and Prime Minister Tony Abbott among the dignitaries to welcome HMAS Canberra into the Australian Navy.

Commanding Officer Jonathan Sadleir officially commissioned HMAS Canberra on behalf of the Australian Navy.

The Governor-General said the event marked a major milestone in the history of Australia's defence forces.

"Commissioning is one of the most important ceremonies in the life of a war ship," Sir Peter said.

Governor-General Sir Peter Cosgrove at the commissioning ceremony for HMAS Canberra. ( ABC: Anne Barker )

"Symbolically it marks when a war ship becomes a part of our Navy and that it's entitled to fly the historic white ensign.

"From the date of commissioning, a war ship is recognised under domestic and international law as a sovereign representative of its nation.

"From today, wherever she may travel in the world, Canberra is all-Australian. The ship and her crew are a part of our nation.

"To the crew, when you set sail, you will do so with the admiration and respect of our nation.

"This is now your opportunity to proudly write a new chapter consistent with the finest traditions of the Royal Australian Navy and the wider Australian Defence Force."

The new ship is the third Navy vessel to be named HMAS Canberra and Rear Admiral Stuart Mayer said all crew and officers were aware of its legacy.

"I have no doubt whatsoever that this Canberra will continue the fine tradition established by her predecessors and add further lustre to an already prestigious name for Queen and country," Rear Admiral Stuart Mayer said.

HMAS Canberra to also get humanitarian missions: Abbott

Also known as a Landing Helicopter Dock or LHD, the ship will be able to land 2,000 armed personnel in helicopters and water craft, complete with vehicles, supplies and ammunition.

It is designed to handle combat situations and humanitarian emergencies, and has a flight deck eight storeys above the water.

Mr Abbott said HMAS Canberra was an important part of Australia's defence strategy for the region, and would also be used in humanitarian emergencies.

Prime Minister Tony Abbott arrives for the commissioning ceremony for HMAS Canberra. ( ABC: Anne Barker )

"This is a proud day for our Navy and a proud day for our country and I am so thrilled to be on this mighty ship," Mr Abbott said.

"While Australia always seeks to make friends rather than foes, you never know what's over the horizon.

"The world remains a difficult and dangerous place. Our armed forces deserve the best possible equipment and our friends and neighbours should know they have the strongest possible ally.

"HMAS Canberra is our largest ever war ship and one of the most capable and sophisticated amphibious assault ships in the world.

"It will also be deployed for humanitarian assistance if disaster strikes in the region."

The construction of the Canberra-class LHD has spanned the globe.

Its 230-metre hull was built in Spain in 2008 before being taken to Williamstown, in Victoria, for the fit-out. Sections of the ship have been assembled in other parts of Australia and shipped to Williamstown for installation.

Second Canberra-class ship due in 2016

HMAS Canberra is one of two Canberra-class LHDs with a sister ship in Adelaide still under construction. The HMAS Adelaide, is expected to be ready for commissioning in 2016.

HMAS Canberra Key Statistics Crew: 49 officers, 294 sailors, 50 soldiers

Crew: 49 officers, 294 sailors, 50 soldiers Homeport: Sydney

Homeport: Sydney Launched: February 17, 2011

Launched: February 17, 2011 Commissioned: November 28, 2014

Commissioned: November 28, 2014 Load: 27,500 tonnes

Load: 27,500 tonnes Length: 230m

Length: 230m Draught: 7.08m

Draught: 7.08m Maximum Speed: 20+ knots

Maximum Speed: 20+ knots Maximum Range: 6,000 nautical miles

Maximum Range: 6,000 nautical miles Commanding Officer: Captain Jonathan D Sadleir

The Canberra Class LHDs have been designed to be able to manoeuvre in shallow waters.

They have a large ramp/door at the stern that lowers to allow access for the four LCM-1E amphibious landing vehicles the ship will normally carry.

A 202-metre-long landing deck can support up to four CH-47 Chinook helicopters taking off or landing at the same time.

The Canberra's combined electrical output is the equivalent of 60 Formula One racing cars.

The ship's Amphibious Operations Officer, Major Matthew Singers, said it represented "one of the largest capabilities that's in the Southern Hemisphere".

"It can provide humanitarian aid and disaster relief, and it's been likened to being the Swiss army knife of the ADF's force projection and combat power."

Despite its size, the ship has a crew of just 400, compared to more than 1,000 on some of its predecessors.

Together, the two ships cost more than $2 billion.

HMAS Canberra will stay in its home port in Sydney until it receives its first assignment.