Zlatan Ibrahimovic scored twice to give Milan a 2-1 win over Inter in a dramatic Derby della Madonnina as he marked his return from having coronavirus in style.
The 39-year-old had missed four games and not played for almost a month after contracting COVID-19, but he put Stefano Pioli's men two goals up inside 16 minutes on Saturday.
Romelu Lukaku got Inter back in it before the break but, despite second-half pressure, Antonio Conte's side could not force an equaliser as their four-match derby winning streak was ended.
Milan stunned Inter with two goals in the space of three minutes, both scored by Ibrahimovic.
After being sent through on goal by Hakan Calhanoglu, the Swede drew a clumsy foul from Aleksandar Kolarov and took the resulting penalty himself.
Samir Handanovic dived to his right to make an impressive save, only for Ibrahimovic to convert a left-footed rebound.
Ibrahimovic then struck again after a superb counter-attack that also involved Calhanoglu resulted in Rafael Leao sending in a superb cross from the left, which he impressively converted with a controlled first-time finish.
Lukaku made no mistake in the 29th minute as he tucked in from close range after Gianluigi Donnarumma inadvertently touched Ivan Perisic's driven cross into his path.
Lautaro Martinez then had a header cleared off the line by Simon Kjaer and an even better chance in the air, this time from Lukaku, was somehow sent wide by the unmarked Belgium striker at the end of a breathless first half.
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A third headed chance went begging after the break, Achraf Hakimi off target with a diving effort as Inter upped the pressure, while substitute Rade Krunic fired wide when he should have wrapped up a Milan win at the other end.
There was one more twist when Inter were awarded a penalty when Donnarumma was adjudged to have brought down Lukaku in the closing stages but VAR ruled the striker had strayed offside before the incident as in-form Milan held on to celebrate a famous triumph.
What does it mean? Milan flying
Talisman Ibrahimovic has boosted Milan ever since his January arrival and Pioli has the team flying. They are 20 games unbeaten across all competitions and top of the table with four straight league wins to start the season for the first time since they were coached by Fabio Capello in 1995.
That puts them five points clear of their city rivals already, with Conte unable to secure a victory that would have seen him become the first-ever Inter boss to win his first three Milan derbies.
As if he had never been away, Ibrahimovic took hold of the derby and swung the match in his side's favour. He already has five goals in three games this season and created two chances in addition to his goals. He played the full 90 match despite Pioli saying pre-match he did not know how many minutes the veteran had in his legs and proved inspirational once more.
Lukaku extends streak on mixed night
Inter racked up 19 shots but only six of them were on target, with just one of their nine second-half efforts – a late flick from Lukaku - troubling Donnarumma.
Lukaku was a threat and scored in a third straight Milan derby as well as creating three chances for his team-mates – but aside from his goal he could not convert any of his other seven attempts, including missing a superb headed chance to equalise.
Inter will look to bounce back when they start their Champions League group-stage campaign at home to Borussia Monchengladbach on Wednesday, a day before Milan begin their Europa League round-robin efforts with a testing trip to Celtic.