Atletico Madrid gained a measure of revenge for their defeat by Real Madrid in last season's Champions League final with a derby win away to their rivals.
Reigning La Liga champions Atletico took an early lead at the Bernabeu as Tiago headed in from a corner.
Cristiano Ronaldo, on his return from injury, scored a penalty he had won to bring the teams level soon after.
But Atletico, who had to resist plenty of home pressure, won the game courtesy of Arda Turan's neat finish.
Prior to the game, Atletico boss Diego Simeone had downplayed his side's chances of defending their league crown following a summer exodus that saw five key players from last season's La Liga-conquering team depart the club.
While his current crop of players may lack some of the attacking flair of their predecessors they appear to have quickly picked up the tactical nous and spirit that have become the hallmark of their manager's teams.
Like the 2013-14 side, this Atletico team are also physically imposing, which they demonstrated throughout and notably in the 10th minute when Tiago made his way to the near post to plant a header into the net from Koke's corner.
The goal was also further evidence for the critics, whose knives were still sharp from the way they capitulated at Real Sociedad two weeks ago, that this is a Real team who are only quality so long as the ball is heading in the direction of the opposition goal and not their own.
However, this time Real rallied after going behind and with the returning Ronaldo included in their attack they had the firepower to respond.
As he has done on so many occasions, the Portuguese forward created his own scoring opportunity, by tumbling in the box under minimum contact from Guilherme Siquiera, before converting it by sending goalkeeper Miguel Angel Moya the wrong way.
Ronaldo was also the supplier of two subsequent chances for Karim Benzema, the first of which the Frenchman ruined with a heavy touch when through on goal, the second a header which drew a superb save from Moya.
As the game wore on and Real's frustration grew, so did the visitors' belief and after Turan had flashed one shot past the post in the 73rd minute he went one better three minutes later by sweeping home a neat finish past Iker Casillas.