The Norwegian Cruise Line Holdings (NCLH) brand said the confirmation marked "the continued expansion of the company's growth strategy in the luxury segment".
Two sister ships – Seven Seas Prestige and an unnamed vessel – will launch beforehand in 2026 and 2030 respectively.
Jason Montague, chief luxury officer at NCLH, said: "This new-build order continues our measured, strategic expansion within the luxury space.
“It reflects our confidence in the growing demand for Regent’s best-in-class offering and reaffirms our long-standing partnership with Fincantieri, one rooted in craftsmanship and shared pursuit of perfection.”
Prestige class will be Regent's first new ship class in 10 years following its Explorer class vessels. Seven Seas Prestige will be 40% larger than previous Regent vessels but will accommodate just 10% more guests.
At 77,000 tons and carrying just 822 guests with 630 crew members, the line said the ship offers "one of the highest space-to-guest and crew-to-guest ratios in the cruise industry".
NCLH expects to add 14 additional ships across its three brands – including Norwegian Cruise Line and Oceania Cruises – up to 2036, adding more than 39,200 berths to its fleet.