Inter is in first place with a perfect 12 points after winning all four of its games. Juventus, another strong rival, is second with 10 points after defeating Lazio 3-1 earlier in the day.
On Saturday, Inter Milan clinched the Serie A championship by thrashing AC Milan 5-1 in the Milan derby. Meanwhile, champion Napoli was held to a 2-2 draw at newly promoted Genoa.
Inter is in first place with a perfect 12 points after winning all four of its games, two points ahead of Juventus, its fiercest rival, which defeated Lazio 3-1 in the day's opening encounter.
After suffering a humiliating first loss of the year, Milan is now one point farther back in third place before welcoming Newcastle United in the Champions League on Tuesday.
A brace from Henrikh Mkhitaryan, a rocket from Marcus Thuram, and two late goals from Hakan Calhanoglu and Davide Frattesi helped Inter earn its sixth straight derby victory in all competitions. This came as a result of the majority of the boisterous and packed San Siro crowd.
The performance by Simone Inzaghi's team earned them the victory and solidified their position as early favourites to defeat their regional rivals and win a 20th Scudetto. Last season, they defeated Milan to go to the Champions League final.
Mkhitaryan said to DAZN, "We've begun the season beautifully and we want to keep going.
We're all here to accomplish the same thing, therefore it doesn't matter who plays; the coach will choose the player who gives it their all to earn the second star (on the shirt for 20 championships).
Thuram continued his impressive play in an Inter jersey, and the new player was also essential to Mkhitaryan's goal in the fifth minute.
Inter smash Milan
Malick Thiaw was pushed off by France's Thuram, who then found Federico Dimarco, whose miss-hit shot was assisted by the former Armenia midfielder.
Seven minutes before halftime, Thuram further demonstrated Inter's superiority following a quick breakaway that was begun by Lautaro Martinez. Martinez collected the ball from Denzel Dumfries before cutting inside the helpless Thiaw and unleashing an unstoppable shot from the edge of the box.
With 45 minutes remaining, it appeared that the game was over, but Rafael Leao scored his second goal of the season in the 57th minute after Olivier Giroud had superbly set him up. This cut the margin in half.
Inter's first goal this season was scored by Leao, and Mkhitaryan, who had been set up by Martinez, silenced Milan's boisterous "away" fans with his deflected second of the game as a torrential downpour descended on the San Siro.
Calhanoglu's 79th-minute penalty and Frattesi's skillful stoppage-time finish, who had just scored twice for Italy on Tuesday at the same venue, added salt to Milan and coach Stefano Pioli's wounds.
We don't need to apologise to our fans, in my opinion. Do you believe we intended to hand Inter five goals? Pioli, who in 2023 has dropped every Milan derby by an average score of 12-1, declared this defiantly.
"We're disappointed, but you beg for pardon when you purposefully do nothing,"
Napoli salvage point
Five minutes before halftime, Mattia Bani gave Genoa the lead with a header. Two minutes later, Mateo Retegui of Italy scored the visitors' second goal off a feed from Kevin Strootman.
Since joining Genoa from Boca Juniors in July, Retegui has scored twice, and his goal on Saturday appeared to give Genoa an incredible second victory of the year.
Raspadori, though, scored his first goal of the season in the 76th minute to put Napoli back in the game.
With six minutes left, Politano scored a spectacular volley from Piotr Zielinski's lofted pass to save a point for Napoli.
At Genoa, where the champions rallied from two goals down to rescue a point late in the game, Napoli's title defence continued to falter.
The draw at the Stadio Luigi Ferraris was achieved by goals from Giacomo Raspadori and Matteo Politano, both of Italy, who were defeated by Lazio before the international break. Rudi Garcia's team now trails Inter by five points.
Because many of our players returned from international duty just yesterday, we had extremely little time to prepare for this game, according to Politano, speaking to Sky Sport in Italy.