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. If a given ship was superseded by another, scrapped, or lost at sea, it is then succeeded. Some records for tonnage outlived the ships that set them - notably the SS Great Eastern, and RMS Queen Elizabeth. The term "largest passenger ship" has evolved over time to also include ships by length as supertankers built by the 1970s were over 400 metres (1,300 ft) long. 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. While some of these modern cruise ships were later expanded, they did not regain their "largest" titles.

RMS Atrato was a UK iron-hulled steamship. She was built in 1853 for the Royal Mail Steam Packet Company as a side-wheel paddle steamer, and at the time of her launch was the world's largest passenger ship. In 1870 RMSP traded Atrato in, causing her to lose the status of "Royal Mail Ship". She was converted to a single screw ship with a compound steam engine in 1872, and placed on the Aberdeen Line that chartered her to run to Victoria and New Zealand. In 1880 she was renamed Rochester before sinking four years later in 1884 by running aground.