Both teams had chances to take the lead in the first period, but impressive stops from each goalkeeper kept the scores level at the interval.
Madrid took the lead through Ronaldo early in the second period, but Iago Aspas levelled for Celta moments later.
Madrid secured the points in controversial circumstances, however, as Ronaldo slotted a penalty past Javi Varas with 20 minutes remaining.
Here, Sports Mole dissects the 90 minutes of action between the two La Liga rivals.
On target: 10
On target: 11
Was the result fair?
On the balance of play, it is hard to deny that Madrid did not deserve to pick up all three points. They had a host of chances to take the lead in the first period, but found Varas in fine form. It could and perhaps should have been more comfortable in the final minutes, but they were guilty of poor finishing.
Celta Vigo's performance
Celta were impressive in the opening 25 minutes, but just could not find the back of the net during their best spell of the match. They had their goalkeeper to thank for keeping the scores level at the break, while they just could not find the back of the net in the latter stages. One thing is for certain, they ran Madrid very close this evening.
Real Madrid's performance
Madrid were not at their best this evening, but the facts say that it is another three points. Not only did the result move them into second position in the table, it has just placed a slight bit of pressure on Barcelona. It is the first time in 11 months that they have won six games in succession.
Sports Mole's man of the match
Javi Varas: But for the intervention of the Spaniard, Celta would have been at least 3-0 down at the interval. He made a number of key saves in the second half, but unfortunately could not keep hold of his clean sheet.
Biggest gaffe of the match
Javier Estrada had a productive 90 minutes of action this evening. He was a spectator for large periods of the match, but was quick on the scene when required. Overall, neither side would have had many complaints about his performance.
Celta Vigo: Celta will attempt to return to winning ways when they travel to Deportivo La Coruna in a relegation six-pointer on Friday.
Real Madrid: Madrid will attempt to continue their stunning run of form when they welcome struggling Real Mallorca next Saturday.