Defender Gabbia rose highest to thump home Tijjani Reijnders' free-kick in the 89th minute and give Milan a Serie A win which pulls them out of a miserable early season slump.
Juventus were held to a 0-0 Serie A draw at Empoli on Saturday as Thiago Motta's side dropped more points after their goalless home stalemate against AS Roma before the international break.
Inter and AC Milan on Friday rejected the project to modernise and restructure the iconic San Siro stadium which they share, city mayor Giuseppe Sala announced.
Victor Osimhen has been sidelined by Napoli after the team he fired to Serie A glory just a over year ago left him both off their squad list for the 2024/25 campaign and potentially in season-long limbo.
Belgium striker Lukaku completed a permanent move to Napoli from Chelsea on Thursday, ending a long period of limbo with the Blues.
Inter Milan thrashed Atalanta 4-0 on Friday to move provisionally top of Serie A, while Torino snatched a late 1-0 win at Venezia to continue their positive start to the campaign.
The futures of Napoli striker Victor Osimhen and England international Ivan Toney are set to dominate the final day of the European transfer window on Friday as Chelsea continue their frenzied pursuit of new signings.
Napoli have signed Romelu Lukaku from Chelsea, the Serie A club announced on Thursday, ending the Belgium striker's extended period in limbo with the Blues.
Poland goalkeeper Wojciech Szczesny on Tuesday announced he was retiring from football at the age of 34 less than two weeks after the end of his contract with Juventus.
Simone Inzaghi's side prevailed in a tense but eventful clash at the San Siro thanks to Federico Gatti's own goal eight minutes before half-time
The Serie A title credentials of Inter Milan and Juventus will be on the line on Sunday as two giants of Italian football face off in a San Siro showdown.
Argentina forward Martinez glanced home the decisive goal in the 14th minute of an action-packed contest in Florence in which Nicolas Gonzalez wasted a late penalty for the hosts, who had Inter on the back foot for much of the game.
Nigeria striker Victor Osimhen will leave Napoli this summer and join "either Real Madrid, Paris Saint-Germain or an English club", the Italian club's president and owner Aurelio De Laurentiis said on Friday.
Sardinia was mourning the loss of a sporting deity on Monday after the death of former Italy striker Luigi "Gigi" Riva, who did more than anyone else to put the Italian island on the footballing map.
Napoli put aside their recent troubles on Thursday by reaching the Italian Super Cup final with a convincing 3-0 win over Fiorentina in Riyadh.
A stunning first-half brace by striker Dusan Vlahovic helped Juventus to a 3-0 win over Sassuolo in Serie A on Tuesday as Massimiliano Allegri's side extended their unbeaten league run to 15 games in front of a sold-out home crowd.
The 37-year-old Giroud was in the perfect position to head in their second goal before his brilliant back-heel flick set up Theo Hernandez for the third.
Doubles from Hakan Calhanoglu and Lautaro Martinez and a late strike from Marcus Thuram extended Inter's advantage on Juventus, who host Sassuolo on Tuesday night.
Napoli striker Victor Osimhen has replied angrily to suggestions that he would leave the Serie A side for Saudi Arabia at the end of this season from agent Mamuka Jugeli, who represents club team mate Khvicha Kvaratskhelia.