A late Mohamed Salah goal followed up Virgil van Dijk's first half opening goal and put Liverpool 16 clear at the top of the Premier League, as Jurgen Klopp's side sealed a win that may just have handed them their first top-flight title in 30 years.
It took the home side just 14 minutes to get themselves into the lead, with Virgil van Dijk overpowering the United defence with ease to convert a Trent Alexander-Arnold corner.
United responded by falling to pieces, and only some excellent last-ditch defending from Luke Shaw prevented Sadio Mané from poking in a second. VAR and the offside flag then took to the stage, respectively ruling out goals from Roberto Firmino and Georginio Wijnaldum - the former in controversial fashion, for an earlier foul on David de Gea.
Anthony Martial and Andreas Pereira gave the visitors a glimmer or two of hope as half-time approached, but ultimately they were exceptionally lucky to remain in the game at all - even more so after Mané forced a terrific one-on-one stop from De Gea on the brink of the whistle.
Mohamed Salah fluffed another great Liverpool chance as the second half resumed with more of the same, before Jordan Henderson rattled the post with a powerful left-footed effort, in a game that looked increasingly as if it just could not be killed off by the home side.
The visitors crept back in throughout the final half hour, and Anthony Martial blasted over after some excellent link-up play with Pereira. For all the huff and puff, however, you'd be hard pushed to call the game 'narrow' given the overall balance of play, and it was the Reds who had the much-deserved final say.
The decisive goal came in stoppage time, when Alisson found Salah with a long-ball over the United defence, and the Egyptian finished off the game with his first ever goal against United.
Key Talking Point
For Liverpool, everything this season comes secondary to winning the Premier League title. They want it badly; perhaps worse than any team has in the competition's history, and came into this one with another chance to stretch their already-unthinkable lead even further.
With Manchester City dropping points and Leicester falling to defeat earlier in the weekend, they knew they could go 16 clear at the head of the division and put right the one blotch on their near-perfect record so far. They've been so consistent this season that few doubted they would do so.
It perhaps wasn't as comfortable as it should have been considering their overall dominance of the game, but once again they rose to the occasion and got there. They're simply incapable of dropping points at present, and no matter what happens in the title race from here on out, you have to imagine their current lead is unassailable.
Starting XI: Alisson (6); Alexander-Arnold
It was a day in which you could argue none of the Liverpool front three hit the heights they are capable of, but nonetheless the show was run by Roberto Firmino, whose intelligent movement and composure on the ball was an invaluable asset in his side's control of the game.
Roy Keane on disallowed Firmino goal:— Anfield Edition (@AnfieldEdition) January 19, 2020
“Why they’ve disallowed that goal is beyond me.”
Firmino should be arrested and jailed for life. How can you disrespect Wan Bissaka like that. Man did Bissaka dirty #LIVMUN— Benaiah (@kwamebenaiah) January 19, 2020
Firmino is a brilliant player. The doesn't even like to stats pad— Soji (@soji_surge) January 19, 2020
His Anfield account for the season looked as if it had been opened in the first half, only for a cruel and arguably harsh VAR intervention, but he kept his head up and turned in a trademark performance. Regardless of his criticised goal return, he is the gravitational centre of this Liverpool team and the nucleus of their success.
Other than perhaps Van Dijk, he is the one player Liverpool could not afford to lose under any circumstances - and don't they just know that.
Key Talking Point
As much as they would have been told otherwise, United had little to lose as they travelled to Anfield, against a Liverpool team had not lost there in close to 18 months. Any sort of positive performance would have been a positive; unfortunately that was not forthcoming.
No one can take a candle to Liverpool at their best at present, but United's limp subservience, even if it was interspersed with the odd hint of exuberance, made it a simple task. The defeat in itself won't be much of a concern, but the lack of desire to challenge and take the game to their famous rivals will be.
Only Liverpool's profligacy and a couple of tight decisions prevented this one from getting out of hand for United, and that's something they will know they have to take a lesson from.
Starting XI: De Gea
In truth there weren't too many pass-marks in United's overall performance, but the improvement of the much-maligned Fred was once again evident, as he kept United forward in spite of the difficult circumstances.
In other perspective, Fred serves as a cornerstone on this game. Kudos.— Yoga Mahardika (@yogamahardika) January 19, 2020
Fred & Matic have definitely been our best players today!— Tom Potter (@TPotterz) January 19, 2020
Fred has been our most consistently good player for the last 2-3 months but some people will still chat rubbish! #LIVMUN— Rants (@rantsnbants) January 19, 2020
The Brazilian looks twice the player he once was, and a battling, driving performance on the most difficult stage of them all demonstrated clearly that he could yet be an important part of this United team going forward.
Liverpool travel to Wolves looking to further strengthen their grip on the title on Thursday, before FA Cup action takes them to Shrewsbury Town next weekend.
United, meanwhile, host Burnley on Wednesday before travelling to one of Tranmere or Watford.