Galatasaray have been suspended from European competition for a year for breaching financial fair play rules, Uefa has confirmed.
The club will be excluded from the Champions League or Europa League if they qualify this season or next.
European football's governing body said in January that the Turkish champions had broken regulations on the level of financial losses allowed.
The Istanbul club is currently fifth in Turkey's Super League.
Finishing in that position would leave Galatasaray outside the qualifying places for next season's Champions League and Europa League.
The 2000 Uefa Cup winners have played in the Champions League for the past four seasons, going out at the group stage of this season's competition.
They dropped into the Europa League but lost to Lazio at the last-32 stage.
Galatasaray official Iskender Baydar said that club directors are "examining the text of the decision" and will issue a statement later.