One hundred thousand people flocked to see the offical festive switch-on of the metal structure floating on Rio's Rodrigo de Freitas Lagoon.
The 542 tonne structure, wrapped in 3.3 million light bulbs was the centrepiece of an eight minute fireworks show, which has become one of the city's main tourist attractions.
More than a million people are expected to view the structure before the lights are turned off on Three Kings' Day on January 6.
The Guinness Book of Records lists it as the world's largest floating Christmas tree.
