It also helped the European champions extend their club record winning streak to 18 matches in all competitions and equal the record run of victories set by Barcelona between October 2005 and January 2006.
Elsewhere, a ferocious drive by Jose Maria Gimenez set Atletico Madrid on the way to a 2-0 triumph at Elche that lifted them into second place.
Ronaldo, the inspiration behind Real’s blistering form this season, struck the opening goal from the penalty spot nine minutes before the break after he was felled by Jonny Castro.
While Real constantly looked to push forward, they also found it tough against a well-organised Celta.
There was no stopping Ronaldo though as he blasted a volley from the centre of the penalty area after 65 minutes to make it 2-0 before adding a third goal from close range nine minutes from the end.
Real have 36 points from 14 games, four ahead of Atletico and five in front of Barcelona who host Espanyol on Sunday. –