The Turkish side entered the encounter determined to recover from a disappointing 4-1 home defeat to Barcelona the previous week. They made an immediate impact, taking the lead just 66 seconds after kick-off when Yunus Akgun capitalised on a defensive error by Lille centre-back Alexsandro before firing the ball high into the net.
Lille responded quickly, restoring parity in the seventh minute through 19-year-old winger Soriba Diaoune. The teenager displayed impressive composure as he collected a through-ball from Alexsandro, rounded goalkeeper Ugurcan Cakir and calmly finished into an empty net.
Galatasaray had an opportunity to regain the advantage midway through the first half when goalkeeper Berke Ozer appeared to bring down Osimhen inside the penalty area. However, a video assistant referee review established that Ozer had played the ball, and the penalty decision was overturned.
Diaoune continued to trouble the visitors and completed his brace in the 39th minute. The young winger reacted quickly to a rebound after his initial effort was saved, giving Lille the lead and putting the hosts in a promising position.
However, defensive lapses once again proved costly for the French side. Galatasaray equalised just before half-time when Roland Sallai delivered a dangerous cross into the penalty area, allowing Aleksey Batrakov to head home unmarked.
The visitors carried their momentum into the second half and moved ahead seven minutes after the restart. Lucas Torreira met a corner with a header at the near post, and a final touch from Ozer helped the ball cross the line to give Galatasaray a 3-2 advantage.
Osimhen then delivered the decisive moment shortly after the hour mark, finishing a swift counterattack to extend the visitors' lead. The goal was his first in the Champions League since February and made the victory particularly memorable against a club he previously represented.
The result gives Galatasaray renewed confidence as they seek to establish themselves in the competition. They will next host Stuttgart on Tuesday, November 3, with kick-off scheduled for 17:45 GMT.
Lille, meanwhile, face growing concerns after suffering their second home defeat in the Champions League this season despite taking the lead in both matches. They will travel to Norway to face Bodo/Glimt later on November 3 at 20:00 GMT, hoping to secure their first points of the campaign.
