Ribeiro struck with a 80th-minute tap-in after Vinicius Junior's left-wing cross at Atletico's Independencia stadium here on Saturday, reports Xinhua news agency.
The victory means Flamengo now have 14 points from seven matches, one point more than second-placed Fluminense, who beat Chapecoense 3-1 at home earlier on Saturday.
In the day's only other match, Sport Recife upset nine-time champions Palmeiras with a 3-2 victory away from home.
Sport rose to sixth in the standings, behind fifth-placed Palmeiras on goal difference.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
