MONZA, Italy – In an all-time upset that will go down among the most talked-about legends of Formula One lore, Pierre Gasly took his maiden victory Sunday during an exhilarating Italian Grand Prix at Autodromo Nazionale di Monza.

Driving for Italian-based Scuderia AlphaTauri, Gasly inherited the lead on lap 29 after Lewis Hamilton had to serve a stop-and-hold penalty for entering a closed pit lane, then fended off a furious late-race charge from McLaren’s Carlos Sainz to take the win at his team’s home Grand Prix.

The young Frenchman’s breakthrough victory came in his 55th F-1 start. It was just his second podium finish and his best result since a runner-up in the Brazilian Grand Prix last fall at Interlagos.

“Oh my God, I can’t believe it! What did we just do?!” Gasly radioed to his crew members immediately after crossing underneath the checkered flag.

After being jettisoned from Red Bull Racing to make way for Alex Albon, there were many who thought Gasly’s chance at glory in F-1 had come and gone.

But Sunday’s moment in the sun came amid one of the most remarkable – and most chaotic – races in the history of the Formula One World Championship.

It appeared to be a win going away for Mercedes’ Lewis Hamilton, who led off the starting line and was in prime position to capture his 90th win – putting himself just one behind Michael Schumacher’s F-1 record of 91 grand prix victories.

However, a safety-car period on lap 20 for the stalled car of Kevin Magnussen turned the entire race on its head and took Hamilton out of contention for the win.

As the safety car was being called for, Hamilton’s Mercedes crew elected to bring him in for a pit stop and a fresh set of medium compound Pirelli tires.

The only problem? The F-1 stewards closed pit road to clear the stricken Haas F1 entry of Magnussen due to where it was stopped at the exit of the final corner. That meant that Hamilton, along with Alfa Romeo’s Antonio Giovinazzi, were entering a closed pit lane and copped penalties as a result.

Both drivers eventually received stop-and-hold-plus-10s for their infractions, dropping them to the back of the 17 cars still running after a restart on lap 28 from a red-flag period for Charles Leclerc’s heavy shunt at Parabolica.

That elevated Gasly – who charged past Racing Point’s Lance Stroll and into second behind Hamilton before the latter pitted to serve his penalty – to the lead of the race. It was a position Gasly never relinquished from that point on, leading the final 26 laps en route to victory.

Sainz eventually passed Kimi Raikkonen to assume second on lap 34, but though he closed from more than three seconds back to under a second behind Gasly in the remaining laps, the McLaren driver didn’t have quite enough to challenge for the win in the end and finished .415 seconds back in second place.

Stroll eventually rallied to complete the podium, followed by the second McLaren of Lando Norris and Mercedes’ Valtteri Bottas, who was never a factor at the front of the field after starting second and dropping back to sixth early on.

Renault’s Daniel Ricciardo crossed sixth, followed by a furiously-charging Hamilton, who came from 17th and more than 30 seconds back of the leaders all the way back to finish seventh.

The second Renault of Esteban Ocon, Gasly’s teammate Daniil Kvyat and Racing Point’s Sergio Perez filled out the remaining points-scoring positions in the top 10.

A disastrous home grand prix for Ferrari saw both cars fail to finish, as Sebastian Vettel retired early due to brake failure in addition to Leclerc’s massive crash in turn 11.

The finish:

Pierre Gasly, Carlos Sainz, Lance Stroll, Lando Norris, Valtteri Bottas, Daniel Ricciardo, Lewis Hamilton, Esteban Ocon, Daniil Kvyat, Sergio Perez, Nicholas Latifi, Romain Grosjean, Kimi Raikkonen, George Russell, Alex Albon, Antonio Giovinazzi, Max Verstappen, Charles Leclerc, Kevin Magnussen, Sebastian Vettel.