The huge vessel, named "Harmony of the Seas", has been under construction since September 2013 in the shipyards in Saint-Nazaire.
When finished it will weigh some 227,000 tonnes and measure 362 metres (1,187 feet) in length, 50 metres longer than the height of the Eiffel Tower.
Harmony is also a metre wider than the current twin ocean-going monsters of the pleasure cruise world, which are also 362 metres long.
"Allure of the Seas" and "Oasis of the Seas", the world's biggest cruise ships in current service, are 65 metres wide and come in at 225,000 tonnes a piece. All three belong to Royal Caribbean International cruise lines.
(All photos AFP)
Some 2,500 people are at work building Harmony, which will require 90,000 square metres (968,700 square feet) of carpet and 500,000 litres (132,000 gallons) of paint.
The test runs of the boat are presently set for mid-February 2016 and its first voyage is planned for May next year, a trip from Southampton in Britain to the Spanish city of Barcelona.
The ship will have room for some 6,360 passengers and 2,100 staff members.