Cruise ships are large passenger ships used mainly for vacationing. Unlike ocean liners, which are used for transport, they typically embark on round-trip voyages to various ports-of-call, where passengers may go on tours known as "shore excursions". On "cruises to nowhere" or "nowhere voyages", cruise ships make two- to three-night round trips without visiting any ports of call.

Modern cruise ships, while sacrificing some qualities of seaworthiness, have added amenities to cater to water tourists, with recent vessels being described as "balcony-laden floating condominiums".

As of December 2018, there are 314 cruise ships operating worldwide, with a combined capacity of 537,000 passengers. Cruising has become a major part of the tourism industry, with an estimated market of $29.4 billion per year, and over 19 million passengers carried worldwide annually as of 2011. The industry's rapid growth has seen nine or more newly built ships catering to a North American clientele added every year since 2001, as well as others servicing European clientele.As of 2020, the world's largest passenger ship is Royal Caribbean's Symphony of the Seas.