Harmony of the Seas is an Oasis-class cruise ship built by STX France at the Chantiers de l'Atlantique shipyard in Saint-Nazaire, France, for Royal Caribbean International. With a gross tonnage of 226,963 GT, she is the fourth largest passenger ship in the world, larger than her older sisters Oasis of the Seas and Allure of the Seas, but surpassed by her newer sisters Symphony of the Seas and Wonder of the Seas. Harmony of the Seas is also the second longest cruise ship in the world, being surpassed by Icon of the Seas.

Symphony of the Seas is an Oasis-class cruise ship owned and operated by Royal Caribbean International. She was built in 2018 in the Chantiers de l'Atlantique shipyard in Saint-Nazaire, France, the fourth in Royal Caribbean's Oasis class of cruise ships. At 228,081 GT, she was the largest cruise ship in the world by gross tonnage when built, surpassing her sister ship Harmony of the Seas, also owned by Royal Caribbean International, and surpassed by her sister ship Wonder of the Seas in 2022.