The European champions lead Barcelona by three points at the top of the table and now need to just avoid defeat at Malaga on Sunday to secure their first league title in five years.
Once again Ronaldo made the difference as he blasted into the top corner after just 10 minutes and then added a second with a composed finish early in the second-half yesterday.
Iago Aspas was then controversially sent-off when he saw a second yellow card for diving, but Celta halved the arrears through John Guidetti's deflected effort.
Ronaldo was starting his first La Liga game away from home for nearly two months as in contrast to recent weeks, Zinedine Zidane didn't rotate his starting XI.
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The Frenchman went with the same side that withstood an Atletico Madrid revival to book their place in the Champions League final a week ago.
And he was rewarded early on as Marcelo fed Isco and after he was dispossessed on the edge of the area, Ronaldo smashed the loose ball high into the net.
Celta have now lost eight of their last nine La Liga games having concentrated on their run to the Europa League semi-finals that was ended by Manchester United last week.
Daniel Wass stung the palms of Keylor Navas with a fiercely struck free-kick before Aspas fired just wide twice in quick succession.
And Celta also had a penalty appeal waived away before the break when Raphael Varane handled inside his own area.
Having soaked up that pressure, a deadly Real counter- attack doubled their advantage just three minutes into the second period.
Isco was again the provider as he surged through the midfield before feeding the World Player of the Year to slot home his 13th goal in his last eight games.
Despite their numerical disadvantage, Celta did manage to pull a goal back when Guidetti's effort deflected past the helpless Navas off Ramos.
However, the visitors went straight up the other end and Marcelo's low cross was tapped home by Karim Benzema to restore Real's two-goal cushion.
Ronaldo should have completed yet another hat-trick when he somehow managed to fire wide with the goal gaping before he was replaced with six minutes remaining.