The 4th and 5th Royal-class vessels will be constructed as part of a previously announced agreement between Carnival Corporation (the line's parent company), and Italian shipbuilder Fincantieri S.p.A.
"We are incredibly proud and excited to add two new ships to our already formidable fleet," said Princess Cruises president, Jan Swartz. "With this new ship commitment Princess Cruises will continue to grow and expand globally as the world's destination leader in premium cruising."
The still unnamed 3,560-passenger vessels will join sister ships Majestic Princess (scheduled to debut in China summer 2017), Regal Princess and Royal Princess. They will include Princess Cruises staples such as Movies Under the Stars, the Piazza and balconies in 80% of the staterooms, as well as introduce "new to the line" features.
Carnival Corporation has a total of 16 cruise ships scheduled for delivery between 2016 and 2020. Princess has not revealed where the newbuilds will be based.