Lionel Messi's 600th career goal sank Atletico Madrid 1-0 and ensured Barcelona stretched their lead at the top of La Liga to eight points.
The Argentinian struck with a trademark free-kick as Barca edged past their nearest rivals to take a huge stride towards regaining the title.
Atletico had clawed back the lead to just five points but could not secure the victory which would have reduced the deficit to two.
Barcelona head coach Ernesto Valverde, who saw midfield schemer Andres Iniesta limp off with a hamstring injury before the break, had played down the importance of the match, claiming it would not be a decider.
But his side's victory, and a 34th league game unbeaten, means it is now Barca's title to lose with 11 games remaining.
It was also a first defeat for Atletico boss Diego Simeone in 13 encounters with Valverde.
Atletico were content to play on the break in the early stages so Barca had most of the ball, with Philippe Coutinho forcing an early near-post save from Jan Oblak and Messi hitting a free-kick into the wall.
Messi then somehow wriggled clear of three defenders in a space about the size of a phone box and raced towards goal before driving low too close to Oblak.
But in the 26th minute Messi made the breakthrough after he was brought down by Thomas Partey 25 yards out.
The position of the free-kick was perfect for a Messi special, and he duly wrapped his left foot around the ball, curling it away from the diving Oblak and into the top corner.
It was vintage Messi and a worthy strike to bring up yet another goalscoring milestone.
He now has 539 for Barcelona and 61 for Argentina - in just 747 appearances - and took his tally for this season to 32 in all competitions.
But while Messi was enjoying himself another Barca great, Iniesta, had been limping through much of the first half and eventually had to be replaced by Andre Gomes after 35 minutes.
Treble-chasing Barca announced that he would need to undergo more tests to determine the extend of the problem.
Coutinho twice drew saves from Oblak and Gerard Pique headed over from a corner but Barca could not find a second before the interval.
Atletico, knowing defeat would all but end their title hopes, came out on the attack in the second half.
Antoine Griezmann, with seven goals in his previous two matches, got his first sight of goal in the 75th minute but his shot was wild, flying miles over the crossbar.
Luis Suarez had the ball in the net for Barca moments later but his effort was ruled out for offside.
At the other end Angel Correa thought he had snatched a point when he rifled home from close range but Diego Costa had been flagged offside.