Mohamed Salah crowned an outstanding individual display with a hat-trick and an assist as Liverpool recorded their biggest away win against Manchester United.
Liverpool raced into an early 2-0 lead, Naby Keita arrowing Salah's pass home for a fifth-minute opener before Diogo Jota added a second from Trent Alexander-Arnold's cross eight minutes later.
Salah then took centre stage, the Egyptian hitting a rising shot from Keita's cross on 38 minute before he put Liverpool 4-0 up at the break with a crisp finish from Jota's assist.
Paul Pogba was brought on for Mason Greenwood at half-time but any lingering hopes United had of a second-half comeback were squashed when Salah claimed his third and Liverpool's fifth, finishing with aplomb from a sublime Jordan Henderson through-ball.
It was the first hat-trick scored by an away player at Old Trafford in the Premier League since Dennis Bailey for QPR on 1 January 1992.
Cristiano Ronaldo had a goal overturned for offside and Man Utd's misery was compounded on 61 minutes when Pogba was sent off.
Liverpool's second consecutive 5-0 away win puts them in second on 21 points, one point behind leaders Chelsea. Man Utd drop to seventh with 14 points.
See: Man Utd report | Liverpool report
Next fixtures
Man Utd: 30 Oct v Spurs (A)
Liverpool: 30 Oct v Brighton (H)
Match officials
Referee: Anthony Taylor. Assistants: Gary Beswick, Lee Betts. Fourth official: Mike Dean. VAR: Stuart Attwell. Assistant VAR: Marc Perry.
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