This day in history of Ronaldo
The Brazilian was unveiled as a Barca player after completing a move from Paris St Germain for an initial transfer fee of 25 million euros ($28.22 million) that could rise as high as 30 million euros ($33.86 million).
The 23-year-old, who will inherit the number 10 shirt from the departing Argentine Juan Roman Riquelme, was given a hero's welcome by Barca fans packing two sides of the ground.
They were able to see the presentation on giant video screens before watching their new idol run through a range of tricks and flicks on the Nou Camp pitch.
"This is one of the most emotional days in my life," Ronaldinho told the crowd. "I'll do everything to give the fans reason to cheer."
Ronaldinho's decision to join Barcelona in preference to Manchester United or Real Madrid was based in part on the recent experiences of Romario, Ronaldo and Rivaldo -- three Brazilians who all triumphed during their time at the Nou Camp.
"I want to follow in their footsteps," said Ronaldinho. "They are all great players, world champions, and in part they're the reason why I'm here.
"Ever since I was a child I've dreamed of joining Barcelona and now the opportunity has arrived."
Barcelona president Joan Laporta, who promised during the election campaign to sign at least one world class player with a media profile to match, said the arrival of Ronaldinho would help the club recoup their reputation as one of the world game's biggest players.
"Barcelona already has great world renown but Ronaldinho will help project the club's image around the globe," Laporta said.
By Albert Gea