Inter Milan beat city rivals AC Milan 2-1 on Monday to clinch the Serie A title, the 20th time the club has lifted the trophy in its history.
Goals either side of half-time by Francesco Acerbi and Marcus Thuram set Inter on their way, but Fikayo Tomori pulled one back for AC Milan in the 80th minute and each side had a player sent off shortly before the end of the game as tempers flared.
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Inter were able to see out the result, though, and when the whistle blew to end the game they had reached an insurmountable 86 points, 17 clear of Milan with five games to play in the season.
"I told the guys, 'We find ourselves in a situation that's never happened before,'" Inter captain Lautaro Martínez said. "We needed to take advantage of this opportunity, because look around, the entire stadium is ours now."
At the final whistle, a beaming Martinez and teammate Federico Dimarco climbed onto the top of the goal frame at San Siro.
Flares and fireworks were set off in the stands, and the Inter players danced raucously in front of their fans. A banner was unfurled, saying in Italian: "Repeat it to the Madonnina, who are the champions and who the crybabies."
The Madonnina is the statue on top of Milan's cathedral that overlooks the city, and which the derby is named after.
After winning eight other trophies, Simone Inzaghi claimed his first league title as a coach.
"Winning the league with five matches left -- more or less won with nine matches left, today making it mathematically certain -- in a derby, with Milan the home team, that is something that will remain with us," Inzaghi said.
"Everyone gave their very valuable contribution so that we could reach goals like this."
Inter last won the league in the 2020-21 season but failed to replicate that form in the subsequent two years, watching on as Milan and Napoli triumphed in 2021-22 and 2022-23, respectively.
This time around, it has been a dominant campaign for Inzaghi's men, with the Scudetto winners having scored the most goals in Serie A while also boasting the stingiest defence.
Lautaro's impressive return powered the Nerazzurri's attack, scoring 23 goals to be the front-runner for the Capocannoniere, with Marcus Thuram and Hakan Calhanoglu both reaching double figures.
The wing-back system employed by Inzaghi, with stability from Benjamin Pavard, Alessandro Bastoni and Stefan de Vrij allowing Dimarco and Denzel Dumfries to push forward, proved more than effective in nullifying opponents.
With this triumph, Inter move ahead of Milan in Italian league titles, having been tied at 19 ahead of this season. Juventus lead the way with 36 championship wins.
A star is awarded for every 10 Serie A titles. Only Juventus has won more, with a record 36 and thus three stars.
It had long been a matter of when and not if Inter would win Serie A, and they knew that doing so in the Derby della Madonnina at San Siro -- the stadium they share with Milan -- would be extra special, even if they were technically the away team and only one end of the stadium was reserved for their black-and-blue-clad support.
Moreover, Inter had won the past five derby matches, including both legs of the Champions League semifinal last year and a 5-1 humiliation of Milan this season in Serie A.
Inter took the lead in the 18th minute when Pavard nodded on Dimarco's corner for an unmarked Acerbi to head in from close range.
Martinez should have doubled Inter's lead seven minutes later when he was also left woefully unmarked, but the league's top goal-scorer inexplicably fired over the bar from point-blank range.
Milan seemed to draw confidence from that miss and Rafael Leão had a great chance to level following a rapid run on the counter-attack from Tomori, but he fired straight at Inter goalkeeper Yann Sommer.
Thuram came close to doubling Inter's lead, but his effort brushed the outside of the far post.
It was end-to-end action, and Milan captain Davide Calabria also forced a great save from Sommer at the end of the first half.
But clinching the crown seemed inevitable less than four minutes after the restart when Thuram ran onto a long Bastoni ball over the top and feinted around his marker to cut in from the left along the edge of the area and drill into the near bottom corner.
There was a tense finale after Milan pulled one back 10 minutes from time. Sommer did brilliantly to parry Matteo Gabbia's header onto his post, but Tomori nodded in the rebound before grabbing the ball and gesturing frantically to his teammates as he raced back to the center circle, desperate to get the equaliser that would prevent Inter from securing the title.
As tempers flared, a scuffle broke out in stoppage time and Milan's Theo Hernandez and Inter defender Denzel Dumfries were sent off. Calabria was also shown a red card moments later following another scuffle.
Information from the Associated Press was used in this story.