Madrid: Barcelona's 100 per cent start to La Liga season was brought to a stunning end as Celta Vigo thrashed the European champions 4-1 on Wednesday.
Real Madrid took advantage of Barca's defeat to move a point clear of the Catalans at the top of the table thanks to Karim Benzema's double in a 2-1 win at Athletic Bilbao.
Celta sit second, behind Madrid only on goal difference, after comprehensively inflicting Barca's first league defeat since February.
Barcelona slip to fifth as Villarreal's 1-0 win at Malaga also gives them a share of the lead in third.
Former Barca forward Nolito put Celta in front before Liverpool reject Iago Aspas struck twice on the counter-attack.
Neymar pulled a goal back for Barca, but Celta rightly had the final word as John Guidetti rounded off a famous win with the Galicians' fourth nine minutes from time.
It is the third time Barca have conceded four goals in just nine games this season having been thrashed 4-0 by Athletic Bilbao in the Spanish Super Cup and beaten Sevilla 5-4 in the UEFA Super Cup.
"We can only congratulate Celta," said coach Luis Enrique, who left Vigo to take over at the Camp Nou last year.
"They played a very complete game, created chances and won all the one-on-one situations. The level of their football and effectiveness in front of goal was very good."
Celta took the lead on 25 minutes when Nolito found space inside the area and curled the ball perfectly high into the far corner.
Accuracy:
Things got worse for Barca just four minutes later when an error from Gerard Pique allowed Nolito to play in Aspas, who remained calm before expertly clipping the ball over the helpless Marc-Andre ter Stegen.
The hosts had to withstand a brief Barca onslaught at the start of the second-half as Lionel Messi struck the post from Andres Iniesta's cut-back.
Pique then headed just over and Messi saw another powerful effort turned behind by Sergio Alvarez.
Yet, from the resulting corner, Celta's lightning speed and accuracy shone through as Aspas hooked the ball over Dani Alves and sprinted half the length of the field before slotting home his second of the night.
Neymar finally got Barca on the scoresheet as he controlled a fantastic pass from Messi before smashing the ball home.
Yet, Celta needed just two minutes to restore their three-goal lead when former Celtic and Manchester City striker Guidetti took advantage of more slack Barca marking to fire home his first goal in Spanish football.
In Bilbao, Madrid were gifted the lead on 19 minutes when Benzema pounced on an under-hit back-pass from Mikel San Jose to net for the fifth consecutive game. (Photo: AP)
Cristiano Ronaldo's wait to surpass Raul as Real's top-scorer continued as his best effort of the night was beaten away by Gorka Iraizoz moments later.
Athletic grew into the game as the half wore on and only a fine save from Keylor Navas prevented Aritz Aduriz bringing the Basques level before the break.
There was nothing Navas could do to prevent conceding his first goal of the season midway through the second period when Sabin Merino rounded off a fine team move with a diving header at the back post to equalise.
But Athletic were only level for three minutes as they afforded way too much room to Isco on the right as his low cross was swept home by Benzema.
"We showed two sides to our game," said Madrid boss Rafael Benitez.
"In the first-half with a lot of possession we had four or five chances when we could have finished the game and then in the second-half we had to show character and work hard."
Elsewhere, Sevilla's nightmare start to the campaign continued as they remain rooted to the bottom of the table after a 2-0 defeat to promoted Las Palmas, who celebrated their first top flight victory in 13 years.
