The match at Old Trafford saw the home team take the lead twice, courtesy of young striker Rasmus Hojlund, who showcased his talent with a brilliant solo effort for his second goal.
Despite holding the lead, United's defence was their Achilles' heel, allowing Galatasaray to level the score twice through Wilfried Zaha and Kerem Akturkoglu. There were more twists in the game as Mauro Icardi missed a penalty for United and Casemiro received a red card following a mistake by Andre Onana.
However, Icardi redeemed himself, breaking through United's defence and scoring the decisive goal nine minutes from time. This unfortunate loss marks the first time that Manchester United has begun a Champions League group stage with two consecutive defeats.
The defeat puts added pressure on United's manager, Erik ten Hag, as the team currently sit at the bottom of the table, trailing their opponents, Galatasaray, who are in second place, behind group leaders Bayern Munich. This loss compounds United's recent woes, with two consecutive defeats in different competitions and a string of losses this season.