Osimhen opened the scoring for the hosts with a superb shot from inside the box one minute before the half hour mark following a pass from Barış Alper Yılmaz.
The Nigeria international doubled Galatasaray’s lead from a header off Davinson Sánchez’s shot one minute before the break.
The 27-year-old has now registered six goals and three assists in six league appearances for the Yellow and Reds this season.
