This is a timeline of the world's largest passenger ships based upon internal volume, initially measured by gross register tonnage and later by gross tonnage.
This timeline reflects the largest extant passenger ship in the world at any given time.
Some records for tonnage outlived the ships that set them - notably the SS Great Eastern, and RMS Queen Elizabeth.
In the modern era the term has gradually fallen out of use in favor of "largest cruise ship" as the industry has shifted to cruising rather than transatlantic ocean travel.
[1] While some of these modern cruise ships were later expanded, they did not regain their "largest" titles.