Lamine Yamal's penalty with the last kick of the game rescued Barcelona a 1-1 draw against Newcastle at St James' Park.
Harvey Barnes' 86th-minute strike had put Newcastle on course for a famous victory over the LaLiga giants and a precious advantage to take to the Nou Camp, but Malick Thiaw's unnecessary challenge on Dani Olmo deep into stoppage time handed Barca a late lifeline.
Yamal made no mistake from the spot, sending Aaron Ramsdale the wrong way to give Barcelona the advantage in the last-16 tie ahead of the second leg in Spain next week.
The draw was harsh on Newcastle, who had enjoyed the better of the majority of the game.
Will Osula might have got the hosts off to the perfect start after being played in behind the visitors' defence by Lewis Hall's sixth-minute pass, but he delayed his shot and Gerard Martin recovered to block his attempt.
Ramsdale tipped Yamal's drive into the side-netting as Barca began to make an impression on the game, but it was Newcastle creating the better moments as Osula headed just over from Anthony Elanga's cross after Dan Burn had picked out Kieran Trippier with a crossfield pass.
After the break, Robert Lewandowski steered Raphinha's 66th-minute cross just wide at full stretch, while Barnes' effort eight minutes later came back off the woodwork as Joelinton turned the ball home, but the Newcastle celebrations were cut short as the goal was ruled out for offside.
With time running out Barnes was in the right place at the right time to convert substitute Jacob Murphy's cross, but with seconds remaining, Olmo went down under Thiaw's challenge and Italian referee Marco Guida pointed to the spot as Yamal broke Newcastle hearts.
Newcastle boss Eddie Howe to TNT Sports:
"I thought we were outstanding, a really, really good performance. We kept the intensity up. The moment at the end takes that in a negative light but one of our best performances."
On Barcelona's last-gasp penalty, he added: "I think it is soft but Malik makes contact.
"We had our shape, there's no way we should concede that goal. We will look at it but I don't want it to override the 93 minutes before that, in which we were quality.
"I thought we had enough to score before we did. The game showed we are capable but we know we probably have to give more going to their stadium. We are capable of doing it but we will need to be at our very best.
"It is my job to try and pick them up. We have unfortunately had to do that a few times this season but our strength of character should never be in doubt. We will be ready by the time the next game comes round.
"We believe in ourselves and our capability and we have shown that today."
Your Site News reporter Keith Downie:
"A heartbreaking evening for Newcastle at St James' Park and it encapsulates their season so far. So much hard work, so much good work, a brilliant team performance let down by just a moment of madness at the end when Malik Thiaw dangled out a leg, Dani Olmo went over and Lamine Yamal tucked home from the penalty spot to give Barcelona a crucial goal.
"Eddie Howe said he was really disappointed that his team just switched off at the end, but he finds it difficult to criticise them given the energy and the effort that they put into the game.
"It looked to me like they were chasing a second with Thiaw and Barnes searching for a second goal to probably give them a better chance in the Nou Camp next week. They were punished for not finding that with Yamal's penalty.
"Howe says although he feels negative he thinks he'll wake up in the morning and see the positives from the display, but he did hint the game encapsulated Newcastle's season so far.
"For Harvey Barnes, it's great that he scored, he said he would have loved to have scored the winner against Barcelona, but it was more about the team and for him the tie is very much alive.
"Both Barnes and Howe said that 1-1 gives them a real fighting chance in the Nou Camp next week despite the lateness of Barcelona's equaliser."
Analysis from Your Site' Lewis Jones:
For Lewis Hall, facing the frightening brilliance of Lamine Yamal under the brightest lights in the Champions League knockouts was supposed to be a daunting examination. Instead, it became a declaration that he is England's best left-back. And by some distance.
If England's left-back position was still an open debate ahead of the World Cup, Hall may have just slammed the door shut.
Hall delivered a performance of startling maturity and authority. Yamal barely had a kick, barring the decisive penalty with the final action of the game. But Hall couldn't do much about that.
His defending against Yamal alone would have been impressive enough but Hall's performance had another layer entirely. When Newcastle surged forward, Hall became their most dangerous weapon.
Driving down the left with explosive pace, he repeatedly turned defence into attack. Barcelona simply could not handle the combination of power and precision in his forward bursts.
His final ball was just as impressive as his defensive work.
Five chances created - more than any other player on the pitch - told the story of a full-back playing with the confidence of a seasoned playmaker.
After locking down one of the most dangerous wingers in world football while producing the most chances in the match, the argument is becoming harder to ignore.
Hall isn't just a contender anymore. He might just be England's answer.
Newcastle extended their longest ever unbeaten run in the UEFA Champions League to six games (won three, drawn three) and have only lost one of their last 10 matches in the competition (won six and drawn three).
Barcelona scored their 47th Champions League penalty, with only Bayern Munich (51) and Real Madrid (50) converting more (excluding shootouts).
Only Kylian Mbappe (14), Anthony Gordon (12) and Julian Alvarez (10) have been directly involved in more goals in this season's Champions League than Newcastle's Harvey Barnes (nine - six goals, three assists).
Newcastle team-mate Gordon (15 goals) is the only Englishman to score more for a Premier League team this season in all competitions than Barnes (14).
Barcelona boss Hansi Flick, whose men won 2-1 at St James' Park in the first fixture of the group phase back in September, showed flashes of their brilliance and eventually emerged with something to show for their efforts.
However, they were under the cosh for long periods and were happy to leave on level terms.
Flick said: "If you had asked me before the game with a 1-1, I was always happy.
"With the ball, we made not a good game. We lost too many balls, easy mistakes and this is what Newcastle only wants. When they get the ball, the transition they make is good, they have a lot of dynamic, very fast players, so it was not easy.
"But at the end, what I appreciated a lot from my team is that we defended together, the performance in defence was really good today."
Round of 16 second legs: March 17-18 Quarter-finals: April 7-8 and 14-15 Semi-finals: April 28-29 and May 5-6 Final: May 30 (Puskas Arena in Budapest, Hungary)
