That’s a great question, but it’s a bit broad. “Biggest” can mean several things: longest, largest by gross tonnage (volume), or largest by passenger capacity.
For 2023, the title holders in the main categories were:
Icon of the Seas (Royal Caribbean International) Maiden Voyage: January 2024 (It was delivered in late 2023 and began operations in 2024). Size: Approximately 250,800 Gross Tons. Length: 1,198 feet (365 meters). Passenger Capacity: 7,600 at maximum capacity (5,610 at double occupancy). Why it’s the answer for 2023: While it entered service in 2024, it was the monumental new ship launched and delivered in 2023, making it the biggest news in the cruise industry for the year. It dethroned Royal Caribbean’s own Wonder of the Seas.
Seawise Giant (later known as Jahre Viking, Knock Nevis, Mont) Status: Scrapped in 2010. Length: 1,504 feet (458.45 meters). Note: This ULCC (Ultra Large Crude Carrier) still holds the record for the longest ship ever built. No ship in active service in 2023 surpassed its length.