What a humiliating day for the Barcelona fans as the team drift farther away from the top of the lead table. Real Madrid has won four straight el-Clasico wins for the first time since 1965 as David Alaba and Lucas Vazquez's goals at Camp Nou put even more pressure on Ronald Koeman and Barcelona.
Vazquez scored in stoppage time in the second half to extend Madrid's lead after Alaba took the lead in the first half. Sergio Agüero scored his first Barcelona goal to score in a tense final, but it was an only consolation as Madrid held out.
In a game where clear odds were tight, Sergino Dest missed a once-in-a-lifetime opportunity to put Barcelona in front just before half an hour. He hit Memphis Depay's cross but fired over the crossbar from the center of the box.
Seven minutes later, Madrid took the lead. Alaba recovered the ball on its own surface and started a counterattack that saw Rodrygo and Vinicius Jr. combine before Alaba ended the move with a powerful shot through the goal in the top corner.
Barcelona had chances on both sides of the half. Gerard Pique nodded in a Depay corner before Ansu Fati saw two attempts blocked shortly after the break. His first shot at Thibaut Courtois in the Madrid goal before Ferland Mendy blocked his second chance.
As the game was nearing its climax, Barcelona looked for an equalizer and almost found one in five minutes when Aguero - replacing Fati - stepped onto a Depay cross but couldn't keep his head.
Then, in stoppage time, things came full circle for Real Madrid when Marco Asensio's shot parried into the path of Vazquez, who slid the ball into the top of the net at close range.
Barcelona found time to console themselves when Agüero scored their first goal for the club after a close cross.
With the win, Carlo Ancelotti's men climb to the top of La Liga, while Barcelona drops to ninth place.