Tens of thousands of people poured onto the streets across Greece to celebrate Olympiacos' Conference League title on Wednesday evening.
Playing on home soil in Greece, Olympiacos defeated Italian team Fiorentina 1-0 after extra-time.
Fans in their home town of Piraeus lighted up flares and fireworks of all kinds, turning the night into day, Greek media reported.
"We haven't seen so many people celebrating in 20 years," said an older man said. He recalled a similar enthusiasm after Greece unexpectedly won the Euro 2004 under then German coach Otto Rehhagel.
"Madness everywhere," was the headline in the Greek sports newspaper Protathlitis on Thursday.
The celebrations reached their high point when the Olympiacos team arrived in the centre of Piraeus, where, according to police estimates, around 30,000 fans watched the final on a large screen.
Many arrived at the square in front of the town hall 10 hours before the start of the match to ensure a good view.
The celebrations came to an end at around 6:00 am (0400 GMT) on Thursday. Many people went straight to work, Greek TV stations reported in their morning shows.
The match took place amid tightest security, with the team from Athens' port of Piraeus playing in the home stadium of rivals AEK Athens, and violence an ongoing problem in Greek football.
But there were no reports of violence during the title celebrations.