The UN cultural body, Unesco, highlighted the "extraordinary fusion" of man-made and natural beauty in certifying Rio on the world heritage list during a ceremony held at the Christ the Redeemer statue.
That blend has "created an urban landscape perceived to be of great beauty by many writers and travelers and one that has shaped the culture of the city," the UN said.
Rio got a big tourism boost during the 2014 football World Cup and this August's Olympic Games. However, persistent high crime, last year's Zika epidemic, and political instability have hurt the city's image.
The Unesco status was announced in 2012, but only became official after the Brazilian authorities were given four years to report on their plans for protecting the likes of Flamengo Park, Sugarloaf Mountain, the Corcovado, Copacabana beach, the Botanical Garden and Tijuca forest.