"Very happy to be here, ready for all the challenges to come. A greeting to the fans," Gila said upon landing at Linate, signing his first autographs and posing for photos with supporters.
The move is worth €25m in fixed fees plus a further €5m in potential bonuses, though 50% of that fee will be passed on to Real Madrid under a sell-on clause agreed when Gila first left the Spanish capital for Lazio.
AC Milan have prepared a five-year contract for the defender worth €4.5m net per season, rising over the course of the deal.
Milan are not only targeting high-profile, expensive forwards this summer - the club is also investing in rising talent for the future. The signing of forward Andrej Kostic, 19, from Partizan Belgrade has been finalised on a permanent basis.
Young but already experienced, Kostic has four caps for Montenegro and scored 10 goals in Serbia's top flight last season, with his path at Milan likely to begin with the club's second team.
Both players arrived in Milan on the same evening, with Kostic also posing for his first selfies as a Rossoneri player. Gila's arrival gives new head coach Ruben Amorim a recognised, well-regarded young central defender to build around, having already beaten competition from Napoli and Atalanta to secure his signature, while Kostic represents the kind of long-term investment in emerging talent that has become a hallmark of Milan's recruitment strategy this summer.
Gila made his name at Lazio after arriving from Real Madrid, establishing himself as a regular in the Roman club's defence and catching the eye of several suitors before Milan moved decisively to get the deal done.
He will be available for Milan's pre-season gathering, which begins on Monday, and is expected to compete immediately for a starting role at the heart of Amorim's back line.
Kostic, meanwhile, arrives with a growing reputation in the Balkans, having broken into Partizan's first team quickly enough to catch Milan's attention despite his tender age.
Physically imposing and versatile enough to play as either a lone striker or in support of another forward, he is seen by the club as a project for the medium term rather than an immediate contributor, with his early football expected to come through Milan Futuro before any step up to the senior squad is considered.