Philippe Coutinho hit a hat-trick but could not save Barcelona's unbeaten season as the Catalans were left stunned by an extraordinary 5-4 defeat to Levante.
Ernesto Valverde rested Lionel Messi for his team's penultimate match of the campaign but it was a defensive horror-show that allowed Emmanuel Boateng to score three times and Enis Bardhi twice at the City of Valencia Stadium.
The La Liga and Copa del Rey champions trailed 5-1 after an hour and still came within a whisker of a sensational comeback as Coutinho's second and third goals, and a Luis Suarez penalty, set up a grandstand finish.
But Levante held on for a thrilling victory, which ends their opponents' hopes of becoming the first ever club to finish a 38-game La Liga season as invincibles.
After drawing at home to Real Madrid last weekend, despite playing the second half with 10 men, and thrashing Villarreal, Barcelona sat just two games away from the historical feat.
It was 1932 when the last side, Real Madrid, went unbeaten in the top-flight but even that was across only 18 matches, in a 10-team division.
This was Barcelona's first league loss since slipping up against Malaga on April 8 last year and while it has minimal impact on the table, Valverde will have questions to answer, not least with regards to leaving out Messi.
"We are angry not to have come through this game and not to have the opportunity to finish unbeaten," Valverde said.
"But in a season some matches go your way and some don't. I think this result was harsh in all respects but at other times this season, like in Seville, we could also have lost."
"But this does not take away everything we have done otherwise this season - everything we have achieved in league, the run we managed across two seasons - but, it is a shame."
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