The first of six new Stena Line ferries to be built in China will sail on the Dublin-Holyhead route in early 2020.
Two other 1,000-passenger vessels will enter service on the Belfast-Liverpool route in the same year and in 2021.
Parent company Stena has ordered the construction of six new-generation vessels from the AVIC Shipyard in China and plans to deploy three of the ferries on Irish Sea routes.
The other three will be chartered out to external parties by Stena Line’s sister company Stena RoRo.
Stena Line chief executive Niclas Mårtensson said: “Our Irish Sea routes are strategically very important to Stena Line and our customers, with the freight market between Ireland and UK experiencing significant growth over the last five years.
“That’s why we have invested almost £200 million in our ports and vessels across the region to improve and grow our capacity to offer a frequent, reliable and high-quality service for our freight and travel customers.
“The deployment of three new vessels is a tangible example of our strategic growth plan for the Irish Sea.
“The first of our new vessels will be deployed on the Dublin–Holyhead service planned for early 2020.
“Furthermore, I can also confirm that two other vessels will be assigned to our Belfast-Liverpool service planned for spring of 2020 and early 2021.”
Mårtensson added: “Our new ferries will be among the most energy efficient in the world with significantly lower CO2 emissions per freight unit against comparable tonnage.
“Our aim is to lead the shipping industry in sustainability and digital development and set new industry standards when it comes to operational performance and emissions.
“We are also placing heavy emphasis on developing a range of exciting new digital features which will provide our customers with unique additional services connected with their journey as well as developing a new, integrated digital onboard experience.”
Stena Line trade director Paul Grant added: “This expansion programme comes on the back of the recent purchase of our superfast ships on the Cairnryan-Belfast service which not only enables Stena Line to deliver a high-quality product for freight and travel customers now but also lays the foundation for continued future growth in the region.”