The world's biggest soccer star and his Inter Miami teammates attended a ceremony at the Port of Miami to take part in the naming of the ship, which can carry 7,600 passengers.
The ship, which officially sets sail for the first time this weekend, is the longest in the world at 1,198 feet long.
The eight-time Ballon d'Or winner headlined the awards ceremony hosted by Mario Lopez near the AquaDome. Messi places the soccer ball on top of the stand and begins the traditional move of breaking a champagne bottle towards the bow of a boat.
Messi, who has been named the godfather or 'icon' of the ship, said: “Family is everything to me. We were thrilled to be a part of the world's best family vacation in Miami.
“Everything I saw at Icon of the Seas is next level. There are also experiences that will create memories that the whole family will remember forever.
The Argentine forward was joined on stage by Royal Caribbean Group Chairman and CEO Jason Liberty, Royal Caribbean International Chairman and CEO Michael Bayley and Icon captain Henrik Loy.
Liberty said: “Icon of the Seas is the culmination of more than 50 years of dreaming, innovating and living our mission to responsibly deliver the world's best vacation experiences. She is the ultimate multi-generational family vacation that will forever change the status quo of family travel. All ages on board. Your vacation dreams can come true.
“With Lionel Messi naming the ship, we are thrilled and honored to have such an iconic person bringing memories to millions of people. soccer “He is a person who loves his fans around the world and thinks it is even more important to create iconic memories with his family.”
Icon of the Seas departs Miami on its inaugural voyage, a seven-night Caribbean cruise, on Saturday, January 27th.