Celta Vigo goalkeeper Sergio Alvarez produced a sublime performance to deny Lionel Messi and Luis Suarez from scoring on special nights for both Barcelona stars.
While the former Liverpool striker was looking to mark his Camp Nou debut with a goal, Messi was looking to at least equal the La Liga record with just one goal.
But Alvarez and the woodwork combined to deny Messi and his team-mate as Celta stole a surprise win, their first Liga triumph at Barcelona for 73 years.
Joaquin Larrivey scored the only goal of the game as Luis Enrique's former club returned to haunt him, but it was Alvarez who stole the show with a string of memorable saves.
The defeat also represented a second successive La Liga loss for Barcelona after the Clasico defeat last weekend, and left Real Madrid with a two-point lead at the table summit.
Messi was named Barcelona captain for the night, and he saw Neymar go close twice in the opening stages, with one effort crashing off the crossbar after a tremendous shot.
Pablo Hernandez was shown a 14th-minute yellow card for hauling down Sergio Busquets, and the Celta man was at the centre of his team's first threat on goal when his header was saved well by Claudio Bravo.
But Messi was then denied three times in as many minutes. Firstly, he saw Celta goalkeeper Alvarez turn his 30th-minute effort over the bar after collecting a return pass from Neymar.
Then Jonny Castro turned away another chance by the Argentina international with an unbelievable clearance which struck the crossbar before bouncing way from danger.