Ronaldo appears to have made soccer history after being given a goal by officials who studied a video clearly showing he did not touch the ball.
The tournament has been dotted with decisions about what constitutes an own goal which appear to contradict FIFA's official guidelines, but Ronaldo's is by far the most bizarre.
The Brazil striker claimed the 10th minute goal against Costa Rica on Thursday and it was initially given to him.
After video replays showed Ronaldo did not touch the ball, FIFA gave it as an own goal to defender Luis Marin. Both players had converged on a cross from the left at the same moment just in front of the Costa Rican goal.
On Friday FIFA announced that after its Technical Committee studied video replays, they decided to give the goal to Ronaldo.
The decision raises questions about whether FIFA bowed in the face of protests by their twice World Player of the Year.
FIFA spokesman Keith Cooper said the Brazil striker had insisted "quite vociferously" in the changing room after Thursday's match that he had touched the ball.
Cooper said the technical study group decided "in the way of positive thinking and along the guidelines that we have established for the definition of an own goal" that it should be given to Ronaldo.
Own goals are rare in World Cup finals - there have been only 22 in the tournaments from 1930 to 1998 - and they are often surrounded by confusion about whether the striker or the defender should be credited.
To help sort out the issue, FIFA published guidelines in April 1997. One diagram in the guidelines shows almost exactly the situation surrounding the Ronaldo goal.
A cross from the left and both the defender and the striker go for it close in.
'Smith (the attacker) claims the goal because of his influence on Jones's (the defender's) action - but Smith has not actually touched the ball.
'Clearly a goal cannot be scored by a player who does not touch the ball himself. And Jones has been deliberately actively involved in the incident.
Verdict: Own Goal.'
Three minutes after his first effort, Ronaldo scored a clear-cut second.
Friday's decision has taken his tally to four in three games, level with Jon Dahl Tomasson of Denmark. Miroslav Klose of Germany leads the scorers' list with five goals.