He opened the scoring with a remarkable 12th-minute strike, collecting the ball from a short corner on the left and whipping it just inside the far top corner from 25 yards.
Ronaldinho celebrated as though he had intended it as a shot rather than a cross, and added his second goal, Atletico's third, in the 32nd minute when he fired a 20-yard free-kick all along the ground and into the bottom left corner.
Rever had scored in the 24th minute, between Ronaldinho's first two strikes, and Figueirense had Jackson sent off before the interval.
Former Barcelona forward Ronaldinho completed his treble with a penalty in the 63rd minute.
Bernard and Carlos Cesar completed the rout, with goals in the 68th and 82nd minutes, as second-bottom Figueirense folded.
Fluminense remain six points clear at the top of the table after 28 rounds of matches, scoring a 1-0 home win over Botafogo thanks to Fred's 73rd-minute goal, a close-range finish after a swift break from midfield.
Third-placed Gremio prevailed 2-1 at home against Cruzeiro, coming alive in the second half after trailing at the break to Anselmo Ramon's 28th-minute drive.
Marcelo Moreno equalised with a superb chip in the 67th minute and Marquinhos prodded in the 78th-minute winner.
And Vasco da Gama remain fourth following a 1-0 victory away to an Atletico Goianiense side that finished with nine men.
Defender Gustavo was ordered off in the 23rd minute, shown two yellow cards in the space of seconds as he reacted inappropriately to being called for an innocuous foul.
Vasco da Gama's breakthrough did not come until the 87th minute when Juninho slotted in a tidy finish to a pull-back from the left, and their bottom-of-the-table hosts lost a second man in the 90th minute when Marino jumped in two-footed on the veteran match-winner.
Nautico were 2-1 winners over Corinthians, with Kieza opening the scoring after 31 minutes, and an own goal from Ralf five minutes from the end settling the outcome. Corinthians had drawn level just before half-time through Paolo Guerrero.
Fifth-placed Sao Paulo eased to a 3-0 success at home against Palmeiras. Luis Fabiano scored twice, in the 36th and 70th minutes, but the highlight was provided by a 43rd-minute strike from 35 yards by Denilson, the midfielder on loan from English club Arsenal.
Palmeiras had defender Artur sent off in the 54th minute.
Santos were held 1-1 at home by Internacional, as Bernardo's 16th-minute goal for the hosts was wiped out in the 52nd minute by substitute Cassiano.