The victory extended their lead over second-placed Fenerbahce, who play Monday night, to six points.
German striker Mario Gomez scored in the 77th minute at Galatasaray’s Turk Telekom Arena Stadium.
Besiktas now lead on 76 points. Fenerbahce face fourth-placed Medipol Basaksehir away on Monday, when third-placed Torku Konyaspor host Kasimpasa.
Anadolu Agency