Doing so in front of a record crowd of 67,000, Spanish starlet Alejandro Garnacho helped down Forest and claim the trophy.
Rhys Bennett put the Red Devils in front but Josh Powell levelled the scores at 1-1. Garnacho then took over.
"I think Manchester United have found themselves a new superstar," said talkSPORT's Micky Gray said of the 17-year-old. It was easy to see why.
The tricky winger won and scored a penalty to put his side ahead with 12 minutes to play, and then ended the tie in stoppage time.
The display could well see Garnacho feature in Erik ten Hag's first team next season, with a number of current stars in attendance to see their likely new teammate.
Captain Harry Maguire was at Old Trafford, along with David de Gea, Bruno Fernandes and Scott McTominay, as well as club icons Sir Alex Ferguson and Bryan Robson.
Garnacho received his award as United U18's player of the season pre-match, and him and his teammates were then sent a message by club icon and Youth Cup winner David Beckham.
"30 years [ago] I got reminded of by Gary Neville but I remember how special the night was," Beckham said. "I remember it was actually the most important trophy that I ever won and the most special trophy."
Beckham couldn't make it to the game, but it would have been hard to notice him anyway in the middle of a record crowd.
The 67,492 in attendance smashed the previous record of 38,187 set by Arsenal and Leeds in the 2007 final.
Tickets for the match cost just £1, with all proceeds going to the club's charity foundation.