United's Under 21 side made sure of the title with an incredible 3-2 at Tottenham thanks to Guillermo Varela's injury time winner.
Joe Pritchard's equaliser six minutes from time looked set to put the champagne on ice but Warren Joyce's side, who had led 2-0 through Donald Love and Andreas Pereira, provided a finish typical of United in the dying seconds of a thrilling contest.
The Reds started in determined fashion and took the lead after only five minutes.
A sublime 13-pass move from one end to the other was rewarded when Paddy McNair found Pereira whom in turn picked out Love to rifle home an excellent finish from 18 yards.
Varela then picked out Pereira with a fine cross and the makeshift striker slammed home a volley on the run to double the visitors lead with only 16 minutes played.
Joel Pereira saved well from Harry Winks and Kazaiah Sterling went close with a header before Spurs captain Will Miller drilled a low effort wide of Pereira to halve the deficit on the half hour.
Joel Pereira kept out Miller's prodded effort after Josh Onomah nutmegged Axel Tuanzebe but United hit back strongly and should have made the points safe after half-time.
Love lashed wide from distance before Andreas Pereira and Devonte Redmond also went close whilst Spurs mustered long range efforts through Winks and Anton Walkes.
Substitute Scott McTominay quickly could have extended the lead when played through by Love but Spurs stopper Luke McGee did well to save and Walkes was on hand to clear the loose ball.
Pereira struck the outside of a post as United came close to making sure of the win but, instead, Spurs levelled with six minutes left to play.
Substitute Marcus Edwards burst clear down the right and his resultant cross picked out fellow replacement Pritchard- who scored in the corresponding fixture- to tap in from eight yards.
That set up a grandstand finish as Cameron Borthwick-Jackson, Edwards and Joe Muscatt all might have scored before Varela's late intervention.
Pereira's clever free-kick picked out McNair and, when his shot was blocked, Varela followed up to hammer home a superb strike past McGee to spark scenes of wild celebrations.
It was no more than Joyce's side deserved and was a fitting way to retain the trophy.
United: J Pereira, Varela, Williams, Tuanzebe, Borthwick-Jackson, Love, McNair, El Fitouri, Redmond (McTominay 62), Riley, A Pereira.