Galatasaray entered the match as table toppers with a perfect five wins from five. Fenerbahce trailed Okan Buruk's team by two points, but had won the last derby 1-0 at Galatasaray last season.
Against 'Cimbom', Mourinho's team started well and created plenty of chances, but it was Galatasaray who scored the first goal. Lucas Torreira, the former Arsenal player, volleyed a venomous striker from long range, flying in via the arm of goalkeeper Dominik Livakovic.
A hard-fought match, which saw nine yellow cards, also saw the second goal within half an hour of play. Victor Osimhen set up Dries Mertens, who skilfully tipped the ball over Livakovic and doubled Galatasaray's lead.
Inefficient Fenerbahce
After half-time, it took 15 minutes for Galatasaray to score their third: a fine combination between Gabriel Sara and Torreira ended with a fine goal from the Brazilian Sara.
Edin Dzeko managed to score from the penalty to cut the deficit after a dubious decision, but they didn't have enough as they succumbed to a damaging defeat in the 401st Intercontinental Derby between the top Turkish teams.
Galatasaray won the Super Lig last season with a record 102 points, and Fenerbahce followed with 99 points, a number that would have been enough for the title in any other season in Super Lig history.
