Fiorentina's Nikola Milenkovic scored in the ninth minute, but it was ruled out for offside at AEK Arena in Athens.
Neither side was able to produce a goal in the 90 minutes of regular play and the final went into extra time.
In the 116th minute, Ayoub El Kaabi scored the winning header, assisted by Santiago Hezze.
With the victory, Olympiacos became the first Greek club to win a major European trophy.
AzVision.az
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