The line – the UK’s third largest – described the move as “the biggest and most exciting evolution in the company’s history”.
The change will coincide with Thomson’s transition to Tui later this month.
What was to be the Tui Explorer ship, arriving next year, will now be called Marella Explorer.
Tui Discovery and Tui Discovery 2 meanwhile will become known as Marella Discovery and Marella Discovery 2.
The name Marella, which means “shining sea” in Celtic, was chosen by the company “to reflect its spirit of exploration and discovery across the seas”.
All of the components of a Thomson Cruises holiday will remain unchanged with Marella Cruises, such as tips and service charges included in the price, the line said.
Helen Caron, distribution and cruise director, said: “This is an incredibly exciting time for our business. We’re really proud to offer an experience that guests can, and want to, come back to again and again and moving forward as Marella we’ve got brand new, modern additions to our fleet and more destinations, choice and experiences than ever before, which really reflects our spirit of exploration and discovery within the new brand.”
To celebrate the launch of Marella Cruises, the company has unveiled new itineraries across Asia as part of its winter 2018 programme.
Marella Discovery will sail to 18 new ports of call on 14 new adult-only itineraries, including Colours of the Far East, departing from Bangkok, Thailand and Enchanting Far East, setting sail from Langkawi in Malaysia.
Marella Discovery’s South East Asian adventure will take it to Singapore, Vietnam, Cambodia and Kuala Lumpur. The ship will also sail to India, calling at ports including Mumbai, Mangalore, Mormugao (Goa), Cochin (Kerala) and Colombo (Sri Lanka), and to the Middle East.
Elsewhere, for the first time in the company’s history, two ships will be based in Barbados for winter 2018. Marella Explorer will sail its first ever winter season from there and will be joined by Marella Celebration.