AC Milan were made to pay for a late lapse in judgement as Mauro Icardi’s 92nd minute strike won the 222nd Derby della Madonnina.
After a wasteful opening from both side – which included two disallowed goals – Icardi took advantage of a lapse in judgement from Gianluigi Donnarumma to head home in added time.
The result hands Milan their first loss in Serie A since the opener at Napoli.
The Rossoneri had the first half chance of the game when Suso – often important in this fixture – dragged a shot narrowly wide from 25 yards.
Hakan Calhanoglu had the next attempt a few minutes later, half-volleying wide after his attempted pass was blocked by an Inter defender.
Mauro Icardi had the ball in the net for Inter in the 11th minute, though VAR correctly showed he was offside and the goal was disallowed.
Inter continued to apply pressure, and Gianluigi Donnarumma was required to make a diving save to stop an Ivan Perisic header from a Sime Vrsaljko cross.
Twelve minutes before the break, the Nerazzurri came close again when Milan failed to clear a corner and Stefan de Vrij hit the post with a hooked effort – the ball eventually being cleared.
The game exploded into life in the closing stages of the first half, with Icardi being denied by a fantastic sliding challenge after seemingly being put through on goal.
Milan then had the ball in the net up at the other end as Mateo Musacchio slid in at the back post to turn home a Suso cross that was flicked on, but the goal was once again correctly chalked off for offside.
Then, Matias Vecino should have given Inter the lead after being found in space by Ivan Perisic, but he fired over from near the penalty spot.
Milan had a fantastic opportunity just after the break when Suso dispossessed Kwadwo Asamoah, though the Spaniard was tackled well by Valero as he looked for options.
Politano had a half chance for Inter in the 58th minute when a deep cross found him inside the box, but the former Sassuolo man dragged his volley wide.
The game then became expectedly scrappy considering what was on the line and the tiring legs, however Suso arguably could have done better with his half-volley having been found in space inside the box; instead giving Samir Handanovic an easy save.
In the second minute of added time the Rossoneri were made to pay for some horrendous misjudgement. A ball in from Vecino found Icardi at the far post and with Donnarumma in No Man’s land, he headed into an empty net to win the derby.