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.
“We will go there to win the game,” insisted Ronaldo. “We are Real Madrid, we are the best and we want to be champions.”
Once again Ronaldo made the difference as he took his tally to 13 goals in his last eight games with early strikes in each half.
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.
However, Karim Benzema and Toni Kroos rounded off the scoring to keep Madrid on course for a La Liga and Champions League double.
“We played with incredible attitude and personality,” said Madrid boss Zinedine Zidane.
Ronaldo was starting his first La Liga game away from home for nearly two months as in contrast to recent weeks, Zidane didn't rotate his starting XI.
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.
“He has managed things very well,” Ronaldo added on Zidane.
“I feel good. Everything is decided in the final weeks of the season and I am doing well. I am scoring goals and helping the team.”
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.
However, they eliminated Madrid from the Copa del Rey earlier this season and put the European champions to the test once more.
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.
“We scored early and then had 20 difficult minutes,” added Zidane.
“In the second-half we controlled the game more because the first-half it was end-to-end which isn't our game.”
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 Ronaldo to finish off the inside of the post.
More controversy ensued moments later when referee Juan Martinez Munera showed Aspas a second yellow card for diving when he appeared to have been tripped by Sergio Ramos inside the area.
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.
Even without him, though, Madrid continued to stream forward and Kroos rounded off the scoring with a cool turn and finish two minutes from time.
By Keiran Canning / AFP