The contenders are:
Oasis Of the Seas.
Royal Caribbean Lines. GRT 225282 LOA 1187ft (362m) Passenger capacity: 5412 double occupancy.
Quantum of the Seas
Royal Caribbean Lines. GRT 168666 LOA 1139ft (347,1m) Passenger capacity: 4180 double occupancy.
Queen Mary 2
Carnival Corp. GRT 148528 LOA: 1132ft (345m) Passenger capacity: 2592 double occupancy.
Norwegian Cruise Lines. GRT 145655 LOA: 1068ft (326) Passenger capacity: 3910 double occupancy
Oasis of the Seas and her sister Allure of the Seas really break all records, and dominate in all categories, although Allure is a smidgen larger than Oasis. Newcomer Quantum of the Seas comes in as number 3 in size, although that is only true until her sisters make an appearance.