As the 19-year-old left his rivals stunned again with his precocious brilliance, Australian Oscar Piastri was left pondering how he nearly picked up the most unlikely of podium places, eventually settling for fourth after the most chaotic of races.
Like the rest of the field, though, Piastri, even picking up three places after starting seventh, had been just a bit player as not even a late safety car deployment and then a red flag suspension to inspect a crumbling surface at the final corner of the track could halt the young Mercedes driver.
Antonelli had been leading by 30 seconds and was on course for perhaps the most decisive Monaco triumph this century.
Instead, he had to first hold off his pursuers after the safety car caused by a crash for Lance Stroll, then once repairs had been carried out to the same spot once Charles Leclerc also crashed there, triggering the red flag, he had to endure another standing start with just eight laps left.
Yet Antonelli was coolness personified, again roaring away to win comfortably by over six seconds from all-time great Lewis Hamilton in his Ferrari.
On a big day for Hamilton, watched by his new girlfriend Kim Kardashian in the paddock, the 41-year-old equalled Ayrton Senna's eight podium finishes in the Principality and is now up to second in the championship, even if he's a distant 66 points behind Antonelli.
"It's been an incredible weekend and an incredible race," beamed the youngster, who wasn't even born when an Italian last won in Monaco - Jarno Trulli in 2004.
But Hamilton, the previous youngest Monaco winner when he won in 2008 aged 23, told Antonelli, who'd also been the youngest polesitter, in the cool down room: "That's too many wins now, buddy!"
Red Bull's Isack Hadjar was a distant third, but for a while after the race, Piastri thought he might get promoted from fourth to third as the Frenchman was under under investigation by the stewards.
That had been wholly unlikely when Piastri was lying sixth after the late red flag, but among those ahead of the Aussie, George Russell had to serve a drive-through penalty which eventually left him out of the points, Pierre Gasly also faced a 10-second penalty and Hadjar was being investigated.
"When you gain three positions in Monaco, it's always a good day," smiled Piastri, who even went ahead of his McLaren teammate Lando Norris in the overall standings after the world champion retired with a power unit problem.
Piastri is now on 60 points in fifth, ahead of sixth-placed Norris on 58. Leclerc is fourth on 75, with Russell on 88, Hamilton on 90 and Antonelli 156.
"We did a good job taking advantage of the opportunities that arose in front of us and being smart with the strategy," said Piastri, who couldn't quite make the podium to mark McLaren's 1000th race.
"Securing those 12 points was important, but our pace wasn't very strong and we need to figure out why we had so many difficulties this weekend.
Eventually, the Australian, who'd earlier also been among a swathe of drivers who got five-second penalties for speeding in the pit lane, had to settle for fourth when Hadjar was cleared by stewards over the alleged red flag infringement.
His podium made some amends for Red Bull after Max Verstappen had earlier stalled on the front row at the start and retired after a lap with a power unit issue.
As for Antonelli, even Hamilton could hardly believe his progress. "He's only 19, so just imagine what the future holds for him, it's a real privilege to witness it," smiled the seven-time champion.
"But I'm going to do my best to try and chase him down for the rest of the year."
