Cristiano Ronaldo extra-time header gave Jose Mourinho his first trophy as Real Madrid coach as his side beat Barcelona 1-0 to win the Copa del Rey.
A foul-ridden encounter was decided in the first period of extra-time when Ronaldo powered in his 42nd of the season from Angel di Maria's cross.
Real had Iker Casillas to thank after the keeper denied Lionel Messi and Andres Iniesta with brilliant saves.
It's always better to win than to lose but life is like that - you can't always win
"I am thrilled to win the Copa del Rey - it is something special," said Real coach Jose Mourinho. "It's a fantastic triumph against a great team like Barcelona - and we deserved it."
The Portuguese, who took over at the club in the summer, added: "I came here to do a job and change the mentality of the club. We have started to do that and it's satisfying - but it's just the start."
Ronaldo, the matchwinner, insisted he had always believed the first goal would prove crucial.
"We knew that whoever scored first would win it - and so it proved," he said. "Mourinho has given us a winning spirit and this is a really important trophy for us - it was an objective we had for this season and we have achieved it."
Both Barca's best chances occured late in normal time with the cavaliers from Catalonia prevented from playing their normal game by the dogged and relentless chasing of Real.
Los Blancos gave dangermen Messi, Iniesta, Xavi and David Villa little breathing space for much of the match at Valencia's Mestalla stadium.
As soon as one of the quartet received the ball a Real duo would attempt to dispossess the ball either legally or illegally. The tactics made Barca look laboured.
At no point in the first half did the potent Messi look like scoring his 50th this season, but it was a different tale at the other end for the other goal-machine on the pitch - Ronaldo.
The Portugal midfielder, who scored his 41th this season with a penalty against the Catalan side last Saturday, had three chances to make it 42 in the opening half.
The Real Madrid squad returned to the Spanish capital to celebrate
The first was a shot from a tight angle which defender Javier Mascherano was forced to clear off the line before the £80m-man failed by fractions to get a connection on Mesut Ozil's dinked ball from six yards out.
He came closest to scoring with his third chance of the half when Real's master of ceremonies, Ozil, sent his team-mate clear on the right who then forced a good low one-handed save from 35-year-old Jose Manuel Pinto.
But shortly before the break, it was Ronaldo's compatriot Pepe, again playing in the centre, who came closest to ending the drought when his header from a Ozil delivery hit the inside of the post and flew to safety.
The league leaders improved after the break and they finally pierced the Real defence and found the back of the net with 20 minutes of normal time remaining. Unfortuntely for Guardiola's team, Pedro's finish, following great work from Messi, was ruled offside.
Moments later, Messi was involved in two chances in the space of five minutes.
The Argentine made Casillas work for the first time in the match with a low shot from the edge of the area that the Spaniard dived low to save.
He then fed in Andres Iniesta whose scuffed shot was again brilliantly tipped away by the Real keeper.
The final 15 minutes of normal time witnessed more clear-cut chances than the other 75, with Real twice going close to pinching it. Ronaldo was denied by a brilliant Dani Alves tackle before Di Maria's deflected strike was pushed over by Pinto.
But they did make the breakthrough just before the extra-time interval when the excellent Di Maria delivered a stunning ball from the right which Ronaldo headed back the way it came and over the reach Pinto.
Real substitute Emmanuel Adebayor forced another great save from Pinto before Di Maria was sent off for a second bookable offence with just seconds remaining of the match.
Victory was Real's first over Barca since May 2008 and it meant that coach Mourinho has won a trophy every year since 2003.
The teams next meet in the first leg of the Champions League semi-final on Wednesday 27 April.
"We can take them on over two games; we have just done that," added Mourinho. "There is no reason we can't beat them in the Champions League because we have just drawn once against them and then beaten them."
Barcelona coach Pep Guardiola said: "It's always better to win than to lose but life is like that - you can't always win.
"We will pick ourselves up - of course we will. We are more sad than if we had won, but that's part of the game. These players have been playing together for a long time and we'll bounce back."
