, when the child fell.
Witnesses said the boy was playing with friends he had made on the trip when he went over the cabin railing.
He plummeted into the internal Central Park area of the ship that has bars, restaurants and pubs.
Witnesses said the child fell from his family's cabin on Deck 14 to the atrium on Deck 8.
Staff battled to resuscitate him, but he died before the ship docked on September 8.
Did you witness the incident on the ship? Email worldnews@the-sun.co.uk
It is understood the boy was on the cruise with his family for a birthday celebration.
Passengers waiting to board the ship for its next cruise from Galveston were told it was delayed as an investigation was launched.
Royal Caribbean confirmed a passenger had died on board but did not give any more detail.
In 2019, a 16-year-old fell to his death on the luxury cruise ship while trying to climb from an eighth floor balcony.
Laurent Mercer plunged as he was trying to reach his family’s stateroom as he didn't have his room card.
A look inside Harmony of the Seas dubbed Europe's biggest hotelThe ship was docked at the port of Labadee in Haiti in the middle of a seven-day Caribbean cruise being taken by the boy’s family.
In 2018, British entertainer Arron Hough from Sunderland disappeared on Christmas Day from the Harmony of the Seas as it sailed off Puerto Rico.
And one person was killed and another four injured after a lifeboat suddenly detached from the Harmony of the Seas in 2016.
The accident reportedly happened during a "security exercise" when the 227,000-tonne ship was docked in the French port of Marseilles.
The vessel dropped around ten metres killing a 42-year-old Filipino.
Harmony of the Seas can hold more than 8,000 passengers and crew.
Owned by Royal Caribbean International, the record-breaking ship is higher than a 25-storey building and forth largest passenger ship in the world.
The boat has been compared to a floating city with more than 2,747 staterooms, 20 restaurants, 23 swimming pools and a park with more than 10,000 plants and 50 trees.
It also boasts ‘seven neighbourhoods’ which include a cinema, promenade, sports and youth zones, an entertainment palace and a spa and fitness centre.
At 1,188 feet long, the 16-deck ship is bigger than the Eiffel Tower and is the widest cruise ship ever built at 215 feet.