Besiktas clinched their second consecutive Turkish league title, and the 15th in their history, on Sunday when a 4-0 win at Gaziantepspor put them out of reach of rival Istanbul club Basaksehir with one match left in the season.
Besiktas fans sang victory songs and set off flares and fireworks after the game, waving flags in the club's black-and-white colours from car windows as they drove through the streets of Istanbul and Ankara, honking car horns.
Besiktas, the least decorated yet oldest of the "big three" teams in Istanbul, will now qualify directly for the Champions League while Basaksehir, who are second and four points behind, go into the qualifying rounds.
Besiktas will add a third star to their logo, having reached 15 league titles. A star is awarded for every five titles.
On Sunday, Besiktas took an early lead against 17th-placed Gaziantepspor when Dutch winger Ryan Babel powered a shot past keeper Erten Ersu six minutes in.
Babel set up Oguzhan Ozyakup for a second goal in the 39th minute and Anderson Talisca sealed the victory early in the second half with two goals.
The jubilation of the Besiktas fans was a world away from the mood of third-placed Fenerbahce and fourth-placed Galatasaray, the other two big Istanbul clubs.
Basaksehir, founded in 1990, have clinched their first run at the Champions League, qualifying for the preliminary round after finishing fourth in the league in the past two seasons.