Kimi Antonelli claimed the Formula 1 world championship lead for the first time in his career after taking advantage of a well-timed Safety Car to win the Japanese Grand Prix.
Having dropped from pole position to sixth on the opening lap as Mercedes' start woes continued, Antonelli was running fourth ahead of the sole round of pit stops at Suzuka before a huge moment of fortune turned the race in his favour.
With the trio who were running ahead of him - Oscar Piastri, George Russell and Charles Leclerc - having already pitted, Antonelli was afforded a much quicker stop when Oliver Bearman's heavy crash triggered a Safety Car, giving the Italian the lead upon the restart.
He was faultless from there on, unleashing superb pace over the second half of the race to finish 13 seconds clear of Piastri, who led a much-improved display from McLaren.
Russell, who expressed his frustration over the radio at his own misfortune, eventually had to settle for fourth behind Leclerc after battling the Ferraris in the closing stages.
Antonelli's nine-point advantage over Russell makes the 19-year-old the youngest driver to lead the world championship in the sport's history, with Lewis Hamilton having previously held the record after first topping the standings at the age of 22 in 2007.
The Italian will hold the lead until at least May, with F1 now embarking on a five-week break until the next race in Miami after the cancellation of races in Bahrain and Saudi Arabia as a result of the ongoing conflict in the Middle East.
Antonelli said: "It feels pretty good! Of course, it's too early to think about the championship but we are on a good way.
"I had a terrible start. I need to check what happened. Then I was lucky with the Safety Car to be in the lead but then the pace was incredible.
"It was really nice. The second stint I felt very good with the car. I'm very pleased with that."
Reigning world champion Lando Norris contributed to McLaren's improved display by passing Hamilton in the closing stages to take fifth.
Pierre Gasly continued his strong start to the season by claiming seventh for Alpine after holding off a near race-long challenge from Red Bull's Max Verstappen.
Liam Lawson also benefitted from the Safety Car as he came from 14th on the grid to finish ninth for Racing Bulls, while Esteban Ocon claimed the final point for Haas.
Haas confirmed that Bearman had been cleared following an X-ray of his right knee, with the 20-year-old Brit having appeared in pain as he limped away from the crash.
Having claimed his maiden F1 victory two weeks earlier in China, Antonelli had been impressive all weekend in Japan, edging Russell in practice and then comfortably beating his team-mate to pole after a unsuccessful setup change had put the Brit on the back foot.
However, all of his good work was quickly undone when another terrible start saw him drop to sixth at the start, with Russell also falling back, from second to fourth.
By the time the pit window had opened for a one-stop strategy, Russell had recovered to second and Antonelli to fourth, but McLaren were eyeing victory with Piastri - having quickly reclaimed the lead when Russell momentarily passed him on lap eight - expressing confidence he could hold off the Mercedes.
Attempting to eliminate the possibility of being undercut by Russell, Piastri stopped at the end of lap 18, before Russell followed suit three circuits later, while Leclerc had already pitted from third.
Having been afforded clear air by Leclerc stopping, Antonelli was displaying electric pace as he closed on Russell before the Brit pitted, but then came a moment of race-defining fortune.
Bearman, chasing Franco Colapinto in a battle for 17th on their 21st lap, lost control of his Haas at the Spoon Curve and spun into the barrier at high-speed, almost instantly triggering a Safety Car.
Antonelli was able to pit and retain the lead, while Hamilton also benefitted from having stayed out as he went from sixth before the pit stops to fourth afterwards.
Russell, who already felt hard done by after suffering issues in qualifying in both China and Japan, expressed disbelief over the radio at the timing of the Safety Car, which occurred almost immediately after he had made his stop.
His task was further stiffened as he was overtaken by Hamilton for third at the restart, while he would then drop a further position to Leclerc after suffering an apparent energy deployment issue.
Both Leclerc and Russell would pass the struggling Hamilton, but the latter was denied a podium for the first time this season as the Ferrari held him off over the final laps.
While he had enjoyed major fortune, the way Antonelli sped clear of Piastri in the closing stages suggested he was the faster of the Mercedes drivers on the day.
By recording successive grand prix victories Antonelli achieved something Russell has never managed, laying down a major marker in the early stages of a campaign many expected the Brit to dominate.
While Russell was most vocal about his misfortune over the radio, Piastri had more reason to be frustrated having been in position to seal an unlikely victory before the Safety Car.
The Australian had been unable to start either of the first two races after crashing in Australia and suffering a technical issue in China, but Sunday's performance suggests the reigning constructors' champions will be regularly challenging for victories sooner rather than later.
F1 returns on May 1-3 with the Miami Grand Prix, the season's second Sprint weekend, live on Your Site F1.
