The GTS Constellation is a Millennium class Cruise ship of the Celebrity Cruises cruise line. She is the co-flagship of the Celebrity fleet, along with Century-class ship Century. Her three sister ships are the Infinity, Summit, and Millennium.

She was built at the Chantier de L'Atlantique in St. Nazaire, France. The ship boasts a COGAS power plant of gas turbines and a steam turbine providing up to 60Megawatts for the electric systems and two 19MW Rolls-Royce/Alstom MerMaid azimuth thrusters for propulsion.
Constellation consistently receives top honors from Condé Nast's readers survey, and is currently ranked by readers as the best large cruise ship[citation needed]. She winters in the Caribbean and and summers in Europe with port calls at popular destinations such as Boston, Massachusetts; Bridgetown, Barbados; Charlotte Amalie, US Virgin Islands; Dover, England; and St. Petersburg, Russia.