| Name | Operator | Began operation | Tonnage | Status |
|---|---|---|---|---|
| Oasis of the Seas | Royal Caribbean Cruise Line | 2009 | 225,282 | Operating |
| Oceana | P&O Cruises | 2003 | 77,499 | Operating. Formely: Ocean Princess |
| Ocean Star Pacific | Ocean Star Cruises | 1971 | 23,149 | Operating, * ex Nordic Prince, Carousel, Arielle, Aquamarine |
| OceanBreeze | Dolphin Cruise Lines / Premier Cruise Line | 1992 | 20,204 | Ex-Southern Cross, Calypso, Calypso I, Azure Seas. Scrapped 2003. |
| Ocean Countess | Royal Olympic Cruises, Monarch Classic Cruises | c. 1997 | 17,593 | Formely: Cunard Countess, Awani Dream II, Olympia Countess, Lili Marleen, Ruby, Olympic Countess |
| Ocean Dream | Pullmantur Cruises | 1981 | 35,190 | Operating. Former Tropicale, Costa Tropicale, Pacific Star. |
| Ocean Life | easyCruise | 2008 | 9,878 | Enters service with easyCruise April 2008. Formerly : easyCruise Life, Farah, The Jasmine, Palmira, Natasha, built as Lev Tolstoy. |
| Oceanic | Peace Boat | 2001 | 38,772 | Operating. Formerly: Oceanic, StarShip Oceanic, Big Red Boat 1 |
| Oceanic Discoverer | Coral Princess Cruises | 2005 | 2,000 | Formerly: Oceanic Princess |
| Oceanic Independence | American Hawaiian Cruises / American Global Line | 1974 | 23,719 | Named formerly (1951—1974) and subsequently renamed (1982—2006) Independence, renamed Oceanic (2006) and then Platinum II (2009), sold for scrap in 2008 but remains in mothballs |
| Oceanos | Starlight Cruises | 1952 | 14,000 | Sank off South Africa's eastern coast on 4 August 1991. |
| Ocean Pearl | Quail Cruises | 1970 | 19,300 | Named formerly Song of Norway, Sundream, Dream Princess, Dream, Clipper Pearl, MS Clipper Pacific, Festival. |
| Ocean Princess | Princess Cruises | 2009 | 30,277 | Formerly: R Four, Tahitian Princess. |
| Ocean Princess | Ocean Cruise Lines | 1984 | Sank March 1993 in Amazon | |
| Ola Esmeralda | Ola Cruises | 1966 | 11,209 | Operating. Formerly: Venus and Black Prince. |
| Oosterdam | Holland America Line | 2003 | 81,769 | Operating |
| Oranje | Netherland Line / Lauro Lines | 1939 | 20,117 / 24,377 | Sunk. Built as a passenger liner, was a hospital ship during WWII. Sold to Lauro Lines in 1964, rebuilt and renamed Angelina Lauro. Destroyed by fire on 30 March 1979, in Charlotte Amalie, St. Thomas. Refloated in July 1979, sank in September 1979 in the Pacific Ocean, while on the way to Taiwan to be scrapped. |
| Oriana | Orient Steam Navigation Company | 1973 | 41,910 | Formerly: served as an ocean liner. Retired in 1986. Served as a floating hotel until 2002. Damaged in a storm in 2004, then dismantled. |
| Oriana | P&O Cruises | 1995 | 69,153 | Operating |
| Orient Queen | Louis Cruises | 1968 | 16,000 | Operating |
| Oriental Dragon | Capital Dragon Global Holdings Limited | 1972 | 18,455 | Operating. Formely: Sun Viking, SuperStar Sagittarius, Hyundai Pongnae, Omar III, Long Jie |
| Orion | Orion Expedition Cruises | 2003 | 4,000 | Originally operated by Travel Dynamics International and transferred to Orion Expedition Cruises in March 2005. Currently operating from Australia. |
Read more about this topic: List Of Cruise Ships