* Wales winger nets winner five minutes from time
* Real make light of absence of injured Ronaldo
* Club can still win a rare treble this season (Writes through with details, quotes)
VALENCIA, Spain, April 16 (Reuters) - Gareth Bale raced away to score a stunning late winner as Real Madrid made light of the absence of top scorer Cristiano Ronaldo to beat arch-rivals Barcelona 2-1 to win a riveting King's Cup final on Wednesday.
Wales winger Bale, who joined Real for a world record fee in the close season, galloped down the left wing into the penalty area in the 85th minute at Valencia's Mestalla stadium and slipped the ball superbly between the legs of Barca goalkeeper Jose Manuel Pinto.
Angel Di Maria had put Real ahead in the 11th minute in the 228th meeting between the two sides when he finished off a swift break with a low shot that Pinto could only palm into the net before Marc Bartra headed in from Xavi's corner in the 68th to make it 1-1.
After Bale struck, Barca had a chance to send the match into extra time in the 89th minute when Neymar, the Catalan club's marquee signing of the close season, found space in the area but his stabbed effort crashed back off a post when he had the goal at his mercy.
"I think the team played a fabulous match tonight in a very entertaining game," Real captain Iker Casillas said in an interview with Spanish television broadcaster TVE.
"We are happy for all the fans who came here to Valencia tonight," added the Spain keeper, who was beaten only once, by Bartra's goal, in nine matches in this season's Cup.
"Now we have to enjoy this moment and think about the league and the Champions League."
Bale was the first Welshman to feature in Spain's 'Clasico' between the world's two richest clubs by income and his wonder goal went some way towards justifying the 100 million euros ($138 million) Real paid Tottenham Hotspur to lure him to La Liga.
The 24-year-old, whose season has been disrupted by a series of minor injuries, stepped up to fill the void left by Ronaldo, who has been sidelined by knee and muscle problems in his left leg, and outshone Barca's four-times World Player of the Year Lionel Messi, who again failed to perform on the big stage.
It was Real's 19th victory in Spain's domestic Cup competition, seven fewer than record winners Barca, and their second in four years after they beat the Catalan club 1-0 in the 2011 showpiece.
It was also a first trophy for their Italian coach Carlo Ancelotti in his debut season and his side still have a chance of becoming only the second team after Barca in 2009 to win a treble of La Liga, Champions League and King's Cup titles.
They are second in the domestic league, three points behind leaders Atletico Madrid with five games left, and play holders Bayern Munich in the semi-finals of Europe's elite club competition this month.
"We deserve it because we played better and had more chances," Portugal captain Ronaldo, who was watching the game from the stands, told TVE.
"We are very pleased with the first trophy of the season and we have two more which we will fight for."
For Barca, a nightmare week comes to an end when they were dumped out of Europe by Atletico and suffered a shock 1-0 defeat at Granada in La Liga that left them four points off the top.
Wednesday's reverse marks the first time they have lost three matches in a row since the beginning of 2003 and coach Gerardo Martino looks likely to end his debut campaign with nothing more than the season-opening Spanish Super Cup.
"We had chances, we dominated the game and the ball," Bartra, who was playing in his first 'Clasico', told TVE.
"But they were more efficient," added the centre back.
"We still have league games to play and we will give it everything, which is all we have left."
The Real fans belted out the Spanish national anthem before kickoff on a warm night in Valencia as the Barca fans, many of them proud Catalans, made their habitual attempt to drown it out with a cacophony of boos and whistles.
After Di Maria's opener, Barca saw plenty of the ball as usual but were unable to convert long periods of possession into a goal as Real waited for a chance to break quickly.
On one such foray forward, Isco had a shot brilliantly blocked by Jordi Alba before Messi had a good chance from the edge of the penalty area but sliced his first-time effort wide.
Barca again saw more of the ball in the second half but Real had the clearer chances with Bale and Karim Benzema going close before Luka Modric shaved a post with a long-range strike.
Four minutes later Bale received the ball on the halfway line and left Bartra for dead before homing in on goal and leaving Pinto on the seat of his pants and the travelling Real supporters in raptures. (Reporting by Iain Rogers, Editing by Pritha Sarkar)