Aritz Aduriz and Inaki Williams scored twice in the space of three minutes to stun the visitors, but Lionel Messi’s bludgeoned free kick helped Barcelona force their way back into the game.
Raul Garcia and Ander Iturraspe were both sent off for fouls on Neymar, who was furious at not being given a penalty too, before Messi struck the post in the last minute of stoppage time to leave Athletic with the advantage going into next Wednesday’s second leg.
Aritz Aduriz meets a cross at the far post to head Athletic Bilbao into a 1-0 lead at the San Mames against Barcelona
The 35-year-old wheels away after seeing his close-range header hit the back of the net, beating Marc-Andre ter Stegen
Aduriz is joined by his team-mates as they celebrate in front of jubilant home supporters
Messi cuts a dejected figure as Athletic players celebrate, while Gerard Pique kicks the ball back to the centre circle
Luis Enrique picked his strongest side, anxious to get off to a good start in 2017 as the club continue their battle on three fronts, although the dream of repeating the treble they earned in 2014-15 is fading.
The current Spanish cup holders didn’t get off to the quickest of starts, with Athletic making the first incursion when Mikel San Jose nodded wide of Marc-Andre ter Stegen’s near post.
Barcelona’s German goalkeeper has already suffered at the defensive midfielder’s hands in the San Mames at the start of last season, when his drive from the centre circle beat the out-of-position goalkeeper, during a 4-0 humiliation for the visitors.
Although they hit back with Neymar trying to make inroads down the left, it was Bilbao who drew first blood.
Veteran hitman Aduriz opened the scoring after 25 minutes, nodding home from close range after Barcelona captain Andres Iniesta gave the ball away in midfield. It was a rare mistake from the playmaker, one capitalised on brilliantly by the striker who turns 36 in January.
To watch him play you wouldn’t know it — Aduriz is as lethal as any other forward in the division, even the world, and he turned provider just three minutes later as Athletic stunned Barcelona with a second goal lashed in by Williams.
Inaki Williams lets fly to as he doubles the home side’s lead with a sweet right-footed effort
The striker sends the San Mames stadium into raptures as they take a two-goal lead in their last-16 first leg match
Bilbao keeper Gorka Iraizoz leaps towards the ball but he fails to stop Messi’s free kick finding the back of the net
Messi pumps his fist as he lofted up into the Bilbao night air by Jordi Alba after reducing the deficit to just one goal
ATHLETIC BILBAO: Iraizoz, Boveda, Balenziaga, Laporte, Etxeita, San Jose, Iturraspe, Raul García, Williams (Elustondo 84), Saborit (Muniain 64), Aduriz (Eraso 78)
Subs not used: Etxebarria, Susaeta, Rico, Arrizabalaga
Goals: Aduriz 25, Williams 28
Sent off: Raul Garcia, Iturraspe
BARCELONA: Ter Stegen; Pique, Rakitic (Gomes 70), Sergio, Iniesta, Suarez, Messi, Neymar, Alba, Roberto, Umtiti
Subs not used: Turan, Rafinha, Mascherano, Alcacer, Digne, Masip
Goals: Messi 52
Bookings: Umtiti, Alba, Iniesta, Busquets
Referee: David Fernandez Borbalan
Aduriz was in the thick of it and showed the lesser-discussed dark side of his game when he attacked Samuel Umtiti at a corner, punching the Barcelona defender in the neck.
Winded, Umtiti gasped for breath although the officials did not see the incident properly and ended up booking both attacker and victim.
If that riled up Barcelona, David Fernandez Borbalan’s denial of a penalty to Neymar a few minutes before the break was the proverbial red rag to a bull.
Xabier Etxeita tripped the Brazilian in the area but Borbalan waved away furious Barcelona appeals, before booking Iniesta, Jordi Alba and Sergio Busquets in the space of a minute as the visitors lost their heads.
Neymar went into the tunnel at half-time having words with the referee and emerged from it 15 minutes later doing the same.
Messi got Barcelona back on track early in the second half with a free kick that Gorka Iraizoz should have kept out.
The Basque goalkeeper pushed the ball onto the crossbar and it bounced into his goal before he clawed it out, with the officials correctly awarding the goal, despite his sly attempts to mask it.
The goal masked a below-par display from the Argentine, still a little rusty from his extended break over the Christmas period, while the same could be said of his strike partner Suarez, although Neymar was closer to his dangerous best.
Andres Iniesta is booked as he protests alongside Neymar, Suarez and Messi after Barcelona are denied a penalty
Messi weaves his way past a trio of Athletic Bilbao defenders as he attempts to drag his side back into the fixture
Neymar screams his displeasure at the referee after he is upended yet again by one of the Bilbao stars
Neymar cannot hide his amazement as another of David Fernandez Borbalan’s calls goes against his side
Athletic’s aggression eventually counted against them when Raul Garcia received his marching orders for fouling Neymar, earning his second yellow card, with 15 minutes to go. Boos for Neymar and applause for the battling midfielder followed, exemplifying the tone set by the team’s performance.
Barcelona nearly scored an instant equaliser when Messi danced away from his marker in the box and was poised to pull the trigger, but San Jose’s stunning tackle denied the No 10 in the nick of time.
Another red card for Athletic followed when Iturraspe received his second yellow card for another swipe at Neymar, leaving them to play the final 10 minutes with just nine men. They survived, but to progress they have to go another 90 minutes at the Nou Camp which will likely be just as thrilling — and perhaps just as savage too.
Athletic defender Mikel San Jose puts in a perfectly-timed challenge to deny Messi drawing Luis Enrique’s side level
Aymeric Laporte tries to get his body between Suarez and the ball as the visitors look to create another opportunity
Sergio Busquets buries his head in the pitch as yet another glorious opportunity for Barcelona goes begging
Athletic Bilbao players are followed by the television cameras as they take the applause of the crowd after full time