Carlo Ancelotti's men welcomed the surprise package to the Bernabeu in an unforeseen top-of-the-table showdown, with Michel's men just two points behind the capital giants ahead of kickoff.
Despite Girona's magnificent exploits this season, the visitors were outmuscled and outclassed on the Bernabeu turf, where Vinicius Junior broke the deadlock after just six minutes.
The Brazilian then turned supplier for Bellingham, playing the Englishman through with an exquisite pass from the left, and the Englishman skipped past Paulo Gazzaniga before finishing comfortably.
Bellingham's first of the night represented his 15th goal of the season, and just nine minutes into the second period, he and Vinicius combined in more unorthodox fashion for the hosts' third strike.
Gazzaniga managed to stick a hand out to deny Vinicius, but the ex-Tottenham Hotspur goalkeeper could only parry the ball back into the danger area, and Bellingham quickly arrived on the scene to double his tally for the evening before being withdrawn injured.
Rodrygo also got in on the act just before the hour mark to erase any lingering doubt, although Real missed out on a five-star performance, as substitute Joselu missed an injury-time penalty.
Nevertheless, the four-goal crushing of their closest title challengers saw Ancelotti's men establish a five-point lead at the top of the La Liga standings, while another personal achievement was Bellingham's to celebrate.
The 20-year-old has been breaking records left, right and centre since swapping Borussia Dortmund for the Bernabeu, and with his double on Saturday, he has now scored more goals for Real Madrid in a single season than any other midfielder.
From 29 matches in all tournaments this term, Bellingham has already found the back of the net a sensational 20 times - in addition to laying on eight assists - and he sits two clear of Artem Dovbyk and Borja Mayoral in the race for the Golden Boot.
However, celebration turned to concern for Bellingham shortly after his second goal of the evening, as the former Birmingham City starlet left the field in the 57th minute with ankle discomfort.
Brahim Diaz came on for the stricken Bellingham, who was able to gingerly make his way off the field, and he was seen with an ice pack wrapped around his ankle while watching on from the dugout.
Real Madrid are therefore set to be sweating over the England international's fitness for the first leg of their Champions League last-16 tie with RB Leipzig, which takes place at the Red Bull Arena on Tuesday night.
Los Blancos are already managing without ACL victims Eder Militao, David Alaba and Thibaut Courtois, while Nacho Fernandez also sat out the win over Girona due to a muscular injury,
With none of Nacho, Alaba or Militao available at the weekend, Real were forced to deploy an emergency central pairing of Dani Carvajal and Aurelien Tchouameni, with 19-year-old Jacobo Ramon among the substitutes.