Callum Hudson-Odoi and unbeaten Nottingham Forest stunned Liverpool at Anfield to end Arne Slot's perfect start as Reds boss.
The substitute cut in from the left and curled an inch-perfect shot into the far bottom corner, which Alisson could not reach.
This was their first win at Liverpool in any competition since 1969.
The home side's confidence was high at Anfield coming into the game after three wins out of three without conceding a goal.
And Liverpool had the better chances, certainly in the first half.
The hosts went closest before the break when Luis Diaz chased a lost cause, cut in and hammered a shot against the near post from a tight angle.
Forest keeper Matz Sels pulled off a good save to keep out an Alexis Mac Allister header and got lucky moments later when he almost spilled Diaz's effort into his own net.
But Forest did create more after the break, with Morgan Gibbs-White and Anthony Elanga shooting off target before Hudson-Odoi's beauty.
Forest fans were jubilant and the Liverpool support tried to get their team going, but they did not fashion many clear chances to equalise.
The visitors move into fourth spot in the fledgling Premier League table with two wins and two draws. Liverpool are two places and one point above them.
Flying Forest
Forest boss Nuno Espirito Santo deserves huge credit for their start to the season.
All the talk was of Liverpool's unbeaten start under Slot - but Forest had not lost a Premier League game either.
And now they are the unbeaten ones.
Their first-half performance was solid and unspectacular. They frustrated Liverpool but did not have a single shot before the break.
However, Nuno was brave in the second half, bringing on Hudson-Odoi and Elanga when the temptation might have been to shore things up - and it paid off.
Elanga found Hudson-Odoi, who cut inside Conor Bradley before swinging in his sweet shot into the bottom corner.
Elanga almost doubled their lead late on when he shot straight at Alisson.
But one goal was enough, and they won at Anfield for the first time since the first man landed on the Moon.
Frustrating day for Liverpool
Former Feyenoord boss Slot will have known it would not all be plain sailing in the Premier League.
But the start he had, including the hugely impressive win over Manchester United before the international break, had people favourably comparing his set-up to Jurgen Klopp's.
Patience, passing and build-up is their style now. And for a while, it looked like their patience would eventually be rewarded.
Diaz hit the post, several headers went off target, and Mohamed Salah forced a good save from Sels at his near post.
Slot brought on Bradley, pushing Trent Alexander-Arnold into midfield, and introduced Cody Gakpo and Darwin Nunez as he tried to find the winner.
But in the end, Bradley was beaten for the only goal of the game.
The hosts had one late chance to level when Virgil van Dijk headed over, but many fans were leaving Anfield before the final whistle went to confirm the end of their unbeaten start.
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