Norwegian Escape and Norwegian Bliss will enter service late 2015 and early 2017.
Two more vessels - 164,600 gross tons and 4,200 passengers will be delivered delivery 2018 and 2019. The ships at a budgeted cost of €1.6 billion (£1.3 billion) - will be constructed by the Meyer-Werft shipyard, Papenburg, Germany.
"Norwegian Breakaway and Norwegian Getaway have proven themselves as industry game-changers and are extremely popular with our guests," said Kevin Sheehan, Norwegian Cruise Line's chief executive officer.
"It was only natural that we build on their success with this new order, and further solidifies our long-term growth strategy." commented Kevin Sheehan, CEO Norwegian Cruise.
Bernard Meyer, managing partner, added: "We are thrilled that Norwegian Cruise Line has the continued confidence in Meyer Werft to expand their fleet. We are very proud of our longstanding relationship with Norwegian Cruise Lines."
JULIAN BRAY [ 01733 345581 ], Journalist, Broadcaster, Aviation Security &Operations, Travel / Cruise Industry Expert, Writer and Coach EQUITY, NUJ, Broadcast ISDN changed number 01733 345020) SKYPE: JULIAN.BRAY.UK e&oe A later updated version is always on the Website