GTS Celebrity Constellation is a Millennium-class cruise ship of Celebrity Cruises. She is the co-flagship of the Celebrity fleet, along with Century-class ship Century. She was originally named Constellation, but renamed in May 2007. Her three sister ships are the Celebrity Infinity, Summit, and Millennium. In 2007 Condé Nast Publications reported that Constellation had come top of their Traveler Cruise Poll six times in seven years. During the summer period the ship sails to the Mediterranean and the Caribbean (winter).