Galatasaray's three-match winning streak in the Champions League came to an end in a 1-0 defeat in Istanbul to Union Saint-Gilloise on Tuesday, with Promise David netting the winning goal for the Belgian side.
The loss was the Turkish side's first home defeat since August 2024, and they remain ninth in the standings on nine points while Union bounced back from three successive Champions League losses and are on six points in 18th place.
Galatasaray and Union are top of their respective domestic league standings, but came into Tuesday's clash with contrasting Champions League form.
The visitors, however, came away with a deserved win against a Turkish side missing their main goal threats.
All eight Galatasaray goals in the Champions League had come from two players, Victor Osimhen with six and Yunus Akgun with two, and with both out injured the hosts struggled to break down the visitors' disciplined defence.
Both sides hit the woodwork in a scoreless opening half, Galatasaray's Gabriel Sara had a fierce effort from distance cannon back off the upright and Union defender Ross Sykes hit the crossbar with a header from a corner.
The only goal came in the 57th minute when Raul Florucz's clever reverse pass found the run of Adem Zorgane and his pullback from the byline was side-footed into the net from the edge of the six-yard area by David.
Galatasaray piled on the pressure and Union cleared a Abdulkerim Bardakci header off the line before the hosts had Arda Unyay sent off late on for a second booking and the Belgian side held on to get their campaign back on track.