Mein Schiff Herz (formerly MV Mercury, Celebrity Mercury and Mein Schiff 2) is the second of two Century-class cruise ships operated by TUI Cruises. Built for Celebrity Cruises at the Meyer Werft shipyard in Papenburg, Germany, she was launched on 11 July 1997, and was christened and entered service as MV Mercury on 27 October 1997.

In 2008, after some eleven years in operation as Mercury, she was renamed Celebrity Mercury. In 2011, she was transferred to the fleet of TUI Cruises, a joint venture between TUI AG and Celebrity Cruises' owner Royal Caribbean Cruises Ltd. At the same time, she was renamed Mein Schiff 2.

In January 2019, she was again renamed, as Mein Schiff Herz. Her sister ship Marella Explorer is the former MV Galaxy, also previously operated by Celebrity Cruises.

TUI Cruises

In February 2011 Celebrity Mercury left Celebrity Cruises to be renovated by Imtech and join TUI Cruises' fleet as Mein Schiff 2, alongside Mein Schiff 1, her sister ship, the former Celebrity Galaxy. In May 2015, TUI Group announced that as part of their modernization strategy, TUI Cruises' Mein Schiff 1 and Mein Schiff 2 would be transferred to Thomson Cruises over the next few years.

In March 2018 it was announced by TUI Cruises that Mein Schiff 2 would remain in the fleet and sail under a new name. It was also announced that Mein Schiff Herz will be handed over to Marella Cruises in April 2022.