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.”