Callum Hudson-Odoi's goal gave Nottingham Forest their first league victory at Anfield in 55 years and ended Liverpool's perfect start to life under Arne Slot on Saturday.
Substitute Hudson-Odoi scored the only goal of the game after 72 minutes, capping a lightning Forest counter-attack with a curling strike that went in off a post.
Liverpool had earlier gone close through Luis Diaz as he struck the base of a post in the first half, but they struggled to pose Nuno Espirito Santo's men too many problems in a flat display.
The defeat, which comes after impressive shutout victories over Ipswich Town, Brentford and Manchester United, means Liverpool have lost early ground on Manchester City, who now boast a three-point lead at the top of the Premier League table.
Forest, meanwhile, remain unbeaten in 2024/25 and move up into fourth place with eight points, just one behind Saturday's opponents, who stay second.
How the match unfolded
Diaz had the first real chance of the match when he rattled a post after 16 minutes, dispossessing Ryan Yates at the byline before cutting inside from the left and seeing his shot bounce clear off the woodwork.
Matz Sels proved his worth for the visitors in the first half, making saves at close range to deny Diogo Jota and Alexis Mac Allister, then being forced into action directly from a corner by Trent Alexander-Arnold in the 35th minute.
Sels almost caused Forest's undoing just before half-time as he spilled Diaz's looping header, but his scrambling recovery just prevented the ball from trickling over the line.
Amid an uncharacteristically quiet display, Mohamed Salah came alive in the 51st minute, twisting and turning to fire a shot towards the near post, but once more, Sels proved equal to it.
Anthony Elanga then blazed over as Forest fired Liverpool a warning shot, but Hudson-Odoi went one better with 18 minutes to play.
Cutting inside from the left, he bent an effort towards the far corner, carrying it out of Alisson's reach to stun Anfield and condemn Liverpool to defeat.
Forest defence forms foundations for success
Forest remain unbeaten through their first four Premier League matches of 2024/25 after passing their toughest test yet with flying colours.
While Hudson-Odoi’s strike sealed Forest’s first win away at Liverpool since defeating Bill Shankly’s side 2-0 in 1969, it was their defence that formed the foundations of their success.
Early tests from Salah were dealt with effectively by Alex Moreno and Murillo, who could match the Egyptian for pace down the hosts' right flank when it mattered in the first half.
On the other side, Ola Aina had another stellar performance, notably quelling the threat of Jota, who until Saturday had provided an effective spearhead to the Liverpool attack.
Other than one self-inflicted wobble, Sels also held firm in the Forest goal to deny a string of chances for Liverpool in the first half and a further flurry in the closing stages of the match.
Time after time a usually fluid Liverpool attack stalled on the offence as Nuno's men maintained their excellent start to the new campaign.
Slot handed reality check
Slot’s flying start to life at Liverpool was brought to a sudden halt as their post-international break lethargy was met by an in-form Forest side.
Slot had won his first three matches in charge and, for 72 minutes, looked set to become the first-ever Premier League manager to keep a clean sheet in his first four matches in charge.
His side looked utterly dominant in the first half, with Forest barely getting a sight of goal, but Liverpool lacked that killer instinct to make their control count.
Slot realised his predicament with 30 minutes to go as he made a triple substitution in the hope of inspiring change, but his side only caught on with 10 minutes to go when a last-minute burst of energy proved too little, too late.
Club reports
Liverpool report | Nott'm Forest report
How the match unfolded
Referee: Michael Oliver. Assistants: Stuart Burt, Dan Cook. Fourth official: Anthony Backhouse. VAR: Graham Scott. Assistant VAR: Craig Taylor.
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