Ronaldo will go on trial at a Brazilian sports tribunal for pulling the hair and pinching a defender in a Brazilian league match.
The three-time world player of the year could miss up to three matches if found guilty in next week's trial, the sports tribunal said Thursday.
The 32-year-old Ronaldo was denounced after TV images showed him grabbing the hair and pinching defender Fahel inside the area last Sunday in Corinthians' scoreless draw against Botafogo at Engenhao Stadium.
Ronaldo's actions came as Fahel grabbed the striker's jersey. The referee did not see the play and none of the players received cards. Ronaldo complained he was fouled and deserved a penalty kick.
"Without a doubt, Ronaldo is a phenomenon ... ," sports tribunal prosecutor Paulo Schmitt said. "But all players are equal to the tribunal and when they do something wrong they must be denounced."
Fahel told local media he could testify in favor or Ronaldo if requested.
"I think he was just upset at the time," Fahel said. "What happens on the field should stay there."
Ronaldo returned to Brazilian football in March after more than a year sidelined because of the third serious knee injury of his career. He has scored 10 goals with four-time national champion Corinthians.
Fans having been calling for his return to the national team, but he wasn't summoned by coach Dunga on Thursday for the upcoming World Cup qualifiers and the Confederations Cup. Ronaldo helped Brazil win the 1994 and the 2002 World Cups.