Kobbie Mainoo settled a thrilling Premier League clash at Old Trafford on Sunday with his first-time strike from the edge of the area after defending champions Liverpool had fought back from two goals down.
The victory saw head coach Michael Carrick achieve the target he was set in January when he was handed the job until the end of the season.
Rescuing United's season from freefall, he has led the club to third in the standings and produced statement wins against Arsenal, Manchester City and now Liverpool.
Victory will strengthen calls for Carrick to be given the role on a permanent basis.
"When Michael comes, he came with magic. Alex Ferguson vibes," United forward Matheus Cunha said with reference to the club's iconic former manager.
"At the end of the day, this is just the start of the journey. It's the beginning, a beautiful beginning."
Ferguson had planned to watch the match at Old Trafford but left the stadium and went to the hospital as a precaution when feeling unwell before kick off.
The fact United secured a Champions League return against their fiercest rivals only added to the scenes of celebration after the final whistle. It was the first time United have completed the league double against the Merseysiders since 2015-16.
United are six points ahead of fourth-placed Liverpool with three rounds of the season to go. Last year, they were 42 points behind Arne Slot's title-winning team.
Cunha put United ahead after six minutes with a left-footed strike from inside the box and Benjamin Sesko doubled the lead in the 14th when bundling in from close range.
United's dominance should have produced more goals with Bruno Fernandes wasting a good chance to add a third.
But the game was turned on its head after the break as Dominik Szoboszlai pulled one back for Liverpool two minutes into the second half and then a mix-up in United's defence allowed Cody Gakpo to equalise in the 56th.
United regained composure and Mainoo's strike saw Old Trafford erupt in celebration.
At the other end of the table, Tottenham looked like a team destined to secure survival after they beat a dire Aston Villa 2-1 with first-half goals from Conor Gallagher and Richarlison to move out of the bottom three with their best performance of the season.
Bournemouth had earlier strengthened their unlikely push for Champions League qualification with a 3-0 win against Crystal Palace.
