An ocean liner is a type of passenger ship that was primarily used for transportation across seas or oceans. Ocean liners may also carry cargo or mail, and may sometimes be used for other purposes (such as for pleasure cruises or as hospital ships). The Queen Mary 2 is the only active ocean liner in 2026, serving with Cunard Line.
The category does not include ferries or other vessels engaged in short-sea trading, nor dedicated cruise ships where the voyage itself, and not transportation, is the primary purpose of the trip. Nor does it include tramp steamers, even those that carry limited numbers of passengers. Some shipping companies refer to themselves as "lines" and their passenger ships, which often operate over set routes according to established schedules, as "liners".
While sharing certain similarities with cruise ships, such as comfort and luxuries for passengers, ocean liners must be able to carry passengers from one point to another between continents on a fixed schedule, the priority being to reach the destination rather than just enjoy the voyage, so must be faster and built to withstand the rough seas and adverse conditions encountered on long voyages across the open ocean. A cruise ship will usually travel within a particular region, while occasionally making an ocean voyage for repositioning. To protect against large waves, ocean liners usually have a higher hull and promenade deck with higher positioning of lifeboats (the height above water called the freeboard), as well as a longer bow than a cruise ship. For additional strength, they are often designed with thicker hull plating than is found on cruise ships, as well as a deeper draft for greater stability, and have large capacities for fuel, food, and other consumables on long voyages. On an ocean liner, the captain's tower (bridge) is usually positioned on the upper deck for increased visibility.
The first ocean liners were built in the mid-19th century. Technological innovations such as the steam engine, diesel engine and steel hull allowed larger and faster liners to be built, giving rise to a competition between world powers of the time, especially between the United Kingdom, the German Empire, and to a lesser extent France. Once the dominant form of travel between continents, ocean liners were rendered largely obsolete by the emergence of long-distance aircraft after World War II. Advances in automobile and railway technology also played a role. After Queen Elizabeth 2 was retired in 2008, the only ship still in service as an ocean liner is RMS Queen Mary 2, which was introduced in 2004 and is also the largest ever built.
Ocean liners were the primary mode of intercontinental travel for over a century, from the mid-19th century until they began to be supplanted by airliners in the 1950s. In addition to passengers, liners carried mail and cargo. Ships contracted to carry British Royal Mail used the designation RMS. Liners were also the preferred way to move gold and other high-value cargoes.
The busiest route for liners was on the North Atlantic with ships travelling between Europe and North America. It was on this route that the fastest, largest and most advanced liners travelled, though most ocean liners historically were mid-sized vessels which served as the common carriers of passengers and freight between nations and among other countries and their colonies and dependencies before the dawn of the jet age. Such routes included Europe to African and Asian colonies, Europe to South America, and migrant traffic from Europe to North America in the 19th and first two decades of the 20th centuries, and to Canada and Australia after the Second World War.
Shipping lines are companies engaged in shipping passengers and cargo, often on established routes and schedules. Regular scheduled voyages on a set route are called "line voyages" and vessels (passenger or cargo) trading on these routes to a timetable are called liners. The alternative to liner trade is "tramping" whereby vessels are notified on an ad hoc basis as to the availability of a cargo to be transported. (In older usage, "liner" also referred to ships of the line, that is, line-of-battle ships, but that usage is now rare.) The term "ocean liner" has come to be used interchangeably with "passenger liner", although it can refer to a cargo liner or cargo-passenger liner. In order for ocean liners to remain profitable, cruise lines modified some of them to operate on cruise routes, such as the SS France. Certain characteristics of older ocean liners made them unsuitable for cruising, such as high fuel consumption, deep draught preventing them from entering shallow ports, and cabins (often windowless) designed to maximize passenger numbers rather than comfort. The Italian Line's SS Michelangelo and SS Raffaello, the last ocean liners to be built primarily for crossing the North Atlantic, could not be converted economically and had short careers.
At the beginning of the 19th century, the Industrial Revolution and the inter-continental trade made the development of secure links between continents imperative. Being at the top among the colonial powers, the United Kingdom needed stable maritime routes to connect different parts of its empire: the Far East, India, Australia, etc. The birth of the concept of international water and the lack of any claim to it simplified navigation during this period. In 1818, the Black Ball Line, with a fleet of sailing ships, offered the first regular passenger service with emphasis on passenger comfort, from England to the United States.
In 1807, Robert Fulton succeeded in applying steam engines to ships. He built the first ship that was powered by this technology, the Clermont, which succeeded in travelling between New York City and Albany, New York in thirty hours before entering into regular service between the two cities. Soon after, other ships were built using this innovation. In 1816, the Élise became the first steamship to cross the English Channel. Another important advance came in 1819, when SS Savannah became the first steamship to cross the Atlantic Ocean. She left the U.S. city of the same name and arrived in Liverpool, England in 27 days. Most of the distance was covered by sailing; the steam power was not used for more than 72 hours during the travel. Public enthusiasm for the new technology was not high, as none of the thirty-two people who had booked a seat boarded the ship for that historic voyage. Although Savannah had proven that a steamship was capable of crossing the ocean, the public was not yet prepared to trust such means of travel on an open sea, and, in 1820, the steam engine was removed from the ship.
Work on this technology continued and a new step was taken in 1833. Royal William managed to cross the Atlantic by using steam power on most of the voyage; sail was used only when the boilers were cleaned. However, there were still many skeptics, and in 1836, scientific writer Dionysius Lardner declared that: As the project of making the voyage directly from New York to Liverpool, it was perfectly chimerical, and they might as well talk of making the voyage from New York to the moon.
The last step toward long-distance travel using steam power was taken in 1837 when SS Sirius left Liverpool on 4 April and arrived in New York eighteen days later on 22 April after a turbulent crossing. Too little coal was prepared for the crossing, and the crew had to burn cabin furniture in order to complete the voyage. The journey took place at a speed of 8.03 knots. The voyage was made possible by the use of a condenser, which fed the boilers with fresh water and avoiding having to periodically shut down the boilers in order to remove the salt. This new record was short-lived. The next day, SS Great Western, designed by railway engineer Isambard Kingdom Brunel, arrived in New York. She left Liverpool on 8 April and overtook Sirius's record with an average speed of 8.66 knots. A race for speed was born, and, with it, the tradition of the Blue Riband.