The Portugal star celebrated his Ballon d'Or nomination in stunning style by scoring all three goals in a routine win, which also saw Real equal Barcelona's all-time Spanish record of 18 consecutive wins in all competitions from the 2005-06 season.
The former Manchester United forward netted his first in dubious fashion as he converted a controversial penalty after he was deemed to have been fouled inside the area.
There was little doubt about the other two, though, as Ronaldo shrugged off several uncharacteristic misses to send Real on their way to a comfortable triumph.
Ronaldo scored his second with 25 minutes to go, firing in from the edge of the area, before completing his landmark hat-trick in the dying stages.
Victory sees Real consolidate their place at the top of the table, though all of the attention will be on Ronaldo and whether Carlo Ancelotti's men can break Barca's tally when they host Ludogorets in the UEFA Champions League on Tuesday.
With the record in their sight, Real poured men forward relentlessly right from the start and somehow failed to take a 10th-minute lead.
Sergio Alvarez got down well to keep out a Ronaldo header after he met Toni Kroos' corner with a towering header, and Sergio Ramos – making his 300th Liga appearance for Real – sliced the rebound wide from five yards out.
Ronaldo looked destined to break the deadlock three minutes later as he raced on to James Rodriguez's low cross, but Jonny Castro's last-ditch intervention was timed to perfection.
And the 29-year-old's frustrations grew a few moments later, as his acrobatic scissor-kick landed on the roof of the net.
Ronaldo eventually got his goal, though, as he stroked home a 36th-minute penalty after Castro was adjudged to have tripped him just inside the area.
Real were denied a two-goal margin at the interval, as Alvarez palmed away Rodriguez's controlled 18-yard effort.
Celta looked threatening at the start of the second half, as Fabian Orellana fired agonisingly wide of the right-hand post after skipping past Dani Carvajal.
Real capitalised on that let-off and doubled their advantage in the 65th minute as Ronaldo pounced on a loose bouncing ball just outside the area and fired past the helpless Alvarez.
And Ronaldo completed the scoring with nine minutes to go, tapping in Marcelo's low cross to claim, surpassing Telmo Zarra and Alfredo Di Stefano's hat-tricks haul.
