Barcelona were level in the second period through Marc Bartra, but Bale's late effort secured the trophy for Los Blancos.
Here, Sports Mole dissects the action between the two Spanish rivals.
On target: 4
On target: 7
Was the result fair?
It is a difficult one. Real Madrid were much the better side for long spells of the first period, but Barcelona looked the team most likely to win it after equalising from a Bartra header. Barcelona's willingness to push for a second in normal time proved to be their undoing, however, as Bale raced the length of the field to score the decisive goal late on. It would not have been unjust had the match entered extra time based on events as a whole, but Real Madrid will feel that they did just about enough to win it after 90 minutes.
It has been a truly disastrous last seven days for the Catalan outfit. A treble had still been a possibility last week, but they were eliminated in the quarter-finals of the Champions League by Atletico Madrid last Wednesday before losing to Granada in La Liga at the weekend. Another defeat this evening means that Gerardo Martino's side are facing the grim possibility of a trophiless season. They have struggled to hit top form in recent weeks and that was indeed the case this evening. As expected, they had the majority of the ball, but too often their forward play was predictable, with Real Madrid prepared to sit deep and expose their lack of pace in defensive areas. Martino's decision not to start with either Pedro or Alexis Sanchez was a strange one, with Barcelona not really having a threat in-behind. Lionel Messi and Neymar were also off-colour once more and Xavi and Andres Iniesta could not provide that magic pass. The equaliser arrived in their best spell of the match, but they were simply unable to kick on as Real Madrid countered to devastating effort once more.
Real Madrid's performance
Despite entering the match in better form than Barcelona, the loss of leading scorer Cristiano Ronaldo meant that Real Madrid were the slight underdogs this evening. However, it simply did not show. Di Maria's early strike handed Los Blancos a platform to build from and while they dropped deeper and deeper as the match gathered pace, they always had that pace in the final third. In contrast to recent Clasicos, there was not too much bite in the middle of the park, which allowed the likes of Isco and Luka Modric time and space on the ball. In truth, it was a tactical masterclass from head coach Carlo Ancelotti, who was more than prepared to let Barcelona have possession for long spells. It was not their best performance of the season - far from it - but it was the type of performance that makes them among the favourites for the Champions League this season. There is not another team in European football that has such pace and movement on the counter-attack.
Sports Mole's man of the match
Gareth Bale: Entering this match, Bale had scored 19 times and registered 15 assists for Real Madrid this season, which made criticism of the Welshman strange. It was said that he needed a big moment in a big match to justify his £80m fee. Well, that occurred at the Mestalla. The former Tottenham attacker was heavily involved throughout the 90 minutes and perhaps should have found the back of the net before his late effort. The 24-year-old was not to be denied, however, as he showed incredible strength and power to wrestle past Bartra, before driving into the Barcelona box and finding the bottom corner. It was a moment of magic from the world's most expensive player.
No real surprises that this goes to Neymar, who missed an absolute sitter in stoppage time. It did not quite happen for the Barcelona forward throughout the contest, but he had a wonderful chance to send the match into extra time after being put through inside the Real Madrid box. It looked for all the world as if the Brazilian had turned his effort beyond Iker Casillas and into the back of the net, but it smashed off the post and back into the arms of the Los Blancos goalkeeper. It was unfortunate, but it was a chance that really should have been finished.
Antonio Mateu Lahoz certainly set the tone in the opening 17 minutes this evening by awarding three bookings. Surprisingly for a Clasico, just two more yellow cards arrived in the second period as Mateu kept control of developments at the Mestalla. There were a couple of flare-ups between both sets of players, but the Spanish official was quickly on the scene to calm proceedings. Barcelona also had three or four penalty shouts, but Mateu was right to turn down the calls on each occasion. Clasico referees have been criticised in recent seasons, but it was a mature and composed performance from Mateu this evening.
Barcelona: Barcelona will attempt to get their La Liga challenge back on track when they welcome high-flying Athletic Bilbao to the Camp Nou on Sunday evening.
Real Madrid: Los Blancos have a free weekend in the league, but return to action next Wednesday as they welcome Bayern Munich to the Bernabeu in the first leg of their Champions League semi-final.