The Reds missed the chance to close the gap to the top four when they lost at the Community Stadium.
The first half was a disaster for the Reds, with two poor goals and an inspired performance from the home team.
After 19 minutes, Ibrahima Konate scored an own goal.
In the first half, the Reds conceded two more from corners and both goals were ruled out for being in the correct area.
After Yoane Wissa's second attempt was denied, the Bees forward headed in after the ball was given away by the Reds.
Alex Oxlade-Chamberlain scored within five minutes of the restart after a triple half-time change from a frustrated manager.
The momentum seemed to be with the other team at that time.
Bryan Mbeumo scored after brushing off Konate in pursuit of a long ball.
Their best run in the top-flight for more than 80 years has ended with a six game winning streak.
If they had won, they would have been a point off fourth and the Bees would have been third.
This was another great night under the lights for the Bees, with wins over Manchester United andArsenal, as well as a victory againstLiverpool.
It was their first win over the Reds in over 70 years.
For all of their good work, the defensive performance ofLiverpool was noteworthy.
Konate was unfortunate with the first goal which hit his calf, but that corner came from Mbeumo running through on the counter- attack and Alisson had to bail out the defence.
The visitors were all at sea at the second and third corners.
They made a mistake when HarveyElliott lost the ball attempting a dummy in his own half, which allowed the other man to set up Wissa.
Konate should have been stronger in the closing moments as Mbeumo knocked him off the ball before he scored. It was a bad night for the centre-back on his first appearance since the World Cup.
After winning back-to-back games, this was a disappointment for the team.
This season, they have dropped more points than they did all of last season.
There is more to come.