Liverpool delivered the complete performance and Mohamed Salah became the club's record Premier League goalscorer as Manchester United were overwhelmed at a joyous Anfield.
United's renaissance under manager Erik ten Hag already has the tangible reward of the Carabao Cup but Liverpool unleashed a brutal reality check on their progress with a severe thrashing.
Liverpool took control of what had been a tight game, with Bruno Fernandes and Marcus Rashford missing presentable chances when former Old Trafford target Cody Gakpo applied a smooth finish to Andy Robertson's perfect pass two minutes before the break.
The second half was a tale of sheer joy for Liverpool and unrelenting misery for United, starting after 47 minutes when Darwin Nunez's header diverted Harvey Elliott's driven cross past goalkeeper David de Gea.
Salah bamboozled Lisandro Martinez to play in Gakpo for another classy finish three minutes later before the Egyptian resumed his long-time role of United tormentor by getting on the scoresheet himself.
Salah ended a swift counter-attack by lashing a finish high past De Gea and the rout continued as Nunez flashed another header in from Jordan Henderson's cross.
Salah then scrambled in the sixth to become Liverpool's highest Premier League goalscorer with 129, passing Robbie Fowler. He is also Liverpool's highest marksman against Manchester United with 11 - and 10 of those have come in his past five encounters.
And in a fitting finish, Roberto Firmino - who has announced he is leaving Liverpool at the end of the season - completed a remarkable game by making it 7-0 from close range.
Liverpool are now an ominous presence in the chase for the Champions League places, standing only three points behind Tottenham with a game in hand.
Liverpool find the fire and fury
Liverpool have resembled a shadow of their real selves this season. The old guarantees, such as intensity and firepower, have been missing far too often.
They all returned here - and how - in the most spectacular manner as Manchester United, who have been undergoing a revival this season, were blown away by a team in full cry.
Once Jurgen Klopp's side took control of a tightly contested game just before half-time, they were ruthless. They scored seven, and missed chances to get more.
Klopp wanted this to be a pivotal week in the race for the top four as his team look to salvage something from a season that has, to this point, been below par.
His players responded. Wolverhampton Wanderers were beaten at Anfield and United, to put it mildly, outclassed.
Liverpool won 5-0 at Old Trafford and 4-0 at Anfield in the Premier League last season while United had a 2-1 win at home early in this campaign to get the Ten Hag era going - and this was another remarkable game to add to that catalogue.
Gakpo was on United's wanted list before he moved to Liverpool in January and his two cool finishes showed why Ten Hag was a fan. Nunez demonstrated his growing threat with a double while Salah always rises to the occasion against United and punished them once more.
There was even the perfect finale of a goal in front of the Kop for Firmino, who announced on Friday he would end a great Liverpool career at the conclusion of this season.
Liverpool manager Klopp resisted a fist pump celebration in front of the Kop - but for him, this day could not have gone any better.
