Advantage Atletico as Bayern have no answer to Saul's stunner
Atletico Madrid 1-0 Bayern Munich
In the contest between the two greatest coaches of their generation, portrayed as dark against light with their differing approaches, it was the man in black who shaded it.
This was a bad night for Pep Guardiola, who faces the prospect of having failed to win the Champions League with Bayern Munich before he heads for Manchester City unless he can overturn this deficit against Diego Simeone's tough, committed Atletico Madrid side.
The winning goal from Saul Niguez was simply world class, worthy of claiming any match, let alone a semi-final first leg of this magnitude, but that is no consolation to a disconsolate Guardiola, who was out-thought tactically in the first half and whose team could not find a way through after that.
It looks set to be another Madrid final, with city rivals Real favourites to overcome Guardiola's next charges, denying the Catalan the delicious prospect of facing the team who next employ him.
First, though, he will face the white-heat of recrimination and blame if he fails to get through this test. It could be an uncomfortable end to the season for Guardiola.
This felt like a heavyweight clash from the off; a clash of cultures and the strength of the Bayern bench said it all: Franck Ribery, Mario Gotze and, surprisingly, Thomas Muller took their place among the substitutes for a contest in which Bayern captain Philipp Lahm said they had to score.
Instead, they conceded to one of the best goals the competition has ever seen. The Calderon, already humming, was rocking. Bayern were left reeling.
The goal came after just 11 minutes, with Saul collecting possession deep and turning away from Thiago Alcantara and towards goal. Suddenly he shimmied between Xabi Alonso and Juan Bernat and, as David Alaba shielded and Arturo Vidal slid in, he used the defender as cover to bend a left-foot shot beyond the dive of Manuel Neuer into the corner of the net.
The Atletico fans were delirious. The noise was deafening. Atletico had poured forward as Simeone had demanded. He said they had to win. Now they had their goal - courtesy of a 21-year-old youth product, one of four in the side - and they were also armed with that formidable, daunting defence.
Simeone had ordered his to attack; to strike early and then to dig in and counter quickly. It was a nightmare unfolding for his opposite number.
How would Bayern respond? They are a free-scoring, rip-roaring side, but here they were up against opponents who had conceded just two goals in 10 Champions League home ties and defend with a fierce obduracy.
As much as Bayern, inevitably, dominated possession, there was always the sense they were being sucked in, with Atletico breaking, the ball flicked on and Antoine Griezmann through on goal. Neuer saved with his legs.
There was a penalty appeal for Bayern when a Lahm shot was blocked. The chance was symbolic of everything Bayern tried.
They passed and passed but always found the route before them blocked.
It was Atletico who carried the threat and Bayern had Javi Martinez to thanks for intercepting a clever, goal-bound flick by Koke.
Atletico had now conceded just once in the first half in their last 20 matches, but Bayern began to push hard after the re-start, with Simeone urging the home supporters to crank up the noise once more.
They were momentarily stunned when, out of nothing, Alaba decided to shoot from distance as Atletico backed off. From 40 yards out, his effort caught goalkeeper Jan Oblak by surprise but cannoned back of the crossbar.
Martinez was then picked out from a corner but planted a free header too straight. Kingsley Coman had already sent another header across goal and narrowly wide.
It confirmed that Bayern were back in it, camped in the Atletico half and finally able to turn all that possession into opportunities.
Douglas Costa broke through down the left but lifted his shot over the bar and Oblak then pushed away Vidal's powerful drive.
Finally a chance fell to Atletico, with Griezmann feeding Fernando Torres, who superbly cut inside, only for his shot to rebound back off a post.
Neuer gratefully held the follow-up by Koke. That could have ended it.