The former Fifa World Player of the Year has penned a six-year deal with the Elland Road giants.
The acquisition of the skilful forward completes a remarkable turnaround for the West Yorkshire outfit, who just three years ago were playing League One football.
"This is a dream come true," he told the club's official website.
"Leeds are one of the best teams in the world and I look forward to winning trophies."
Ronaldinho is expected to make his first appearance in a Leeds shirt in this weekend's friendly against Milan. [/url]