Barcelona's title hopes suffered a shock setback as Granada hit back from a half-time deficit to win 2-1 and end a run of 24 successive league defeats against the Catalan giants at the Nou Camp.
Lionel Messi's 26th league goal of the season appeared to have put Barca on course for a victory that would have lifted them above Atletico Madrid and Real Madrid and into top spot in LaLiga.
But Darwin Machis drew eighth-placed Granada level just after the hour and 39-year-old Jorge Molina completed a memorable comeback for the Andalusian side when he headed home the winner with 12 minutes to go.
Barca came into the match with a game in hand on the top two and knowing a win would keep the fate of the title in their hands with five games to go.
Ronald Koeman's men had not lost at the Nou Camp in 13 league matches, winning 10, but draws against the likes of Eibar and Cadiz would have given Europa League quarter-finalists Granada hope of an upset.
That seemed unlikely though when Messi linked up with Antoine Griezmann before drilling a low shot past Aaron Escandell and into the far corner of the net.
But the hosts could not build on their lead and in the 62nd minute Granada drew level when Barca defender Oscar Mingueza was unable to cut out Luis Suarez's through ball and Machis fired past Marc-Andre ter Stegen at his near post.
Granada were not finished there, however, and in the 78th minute the unmarked Molina glanced home Adrian Marin's left-wing cross to seal an unforgettable victory for his side at the Nou Camp.
