Carnival Cruise Line said the girl fell from an upper deck onto a lower deck in the interior atrium of the Carnival Glory around 8am in the US (11pm Saturday, AEST).
Miami Fire Rescue Capt. Ignatius Carroll told the Miami Herald that the exact distance the girl fell had not been determined, but it could have been between six and 15 metres.
Emergency personnel transported the child to Jackson Memorial Hospital’s Ryder Trauma Center, where she died, police said.
It was not immediately clear what caused the fall.
The child’s name has not been released.