Jesse Lingard's extra-time thunderbolt earned Manchester United a record-equalling 12th FA Cup as Louis van Gaal's side came from behind to defeat Crystal Palace 2-1 in Saturday's final at Wembley.
In a rematch of the 1990 final, which United won after a replay, underdogs Palace took the lead in the 78th minute when Jason Puncheon slammed home, only for Juan Mata to equalise less than three minutes later.
With the tie heading towards penalties, substitute Lingard drilled a stunning volley past a motionless Wayne Hennessey in the 110th minute to end United's 12-year wait to lift the FA Cup and give their supporters something to cheer about at the end of a tumultuous season.
"It is fantastic to win this title for the club, for the fans and also for me, because I now have won the cup in four countries, and not many managers have done that," Van Gaal said.
"With 10 players, and we have played Tuesday evening also (beating Bournemouth 3-1), but we have deserved it, I think. It was a super goal, eh?"
Lingard told BT Sport: "I saw it come across and it landed nicely for me. All I had to do was hit it sweet, and luckily I did that. As a sub you always have to be ready. Thankfully I was."
It was United's first FA Cup win since 2004, allowing captain Wayne Rooney and Michael Carrick to complete their domestic medal collections.
The win took United level with Arsenal, winners in 2014 and 2015, as the most successful clubs in the competition's illustrious history.
But while Van Gaal celebrated his first trophy in English football, and United's first major honour since Alex Ferguson retired in 2013, it may not be enough to keep him in a job following the club's failure to qualify for the Champions League. They will play in the Europa League, instead.
Palace manager Alan Pardew, meanwhile, met with FA Cup heartbreak for the third time, having been on the losing side against United with the south London club in 1990 and overseen West Ham's defeat on penalties by Liverpool in 2006.
Pardew celebrated Jason Puncheon's goal with a touchline dance, but within three minutes Palace's lead had vanished.
Rolling back the years, Rooney did superbly to reach the byline on the right before digging out a cross that was chested down at the back post by Fellaini for Mata to strike a volley that rattled between Ward's feet and crept over the line.
United lost Smalling when the England centre-back received a second yellow card for hauling Yannick Bolasie back by his ankle as he lay on the turf.
The teams exchanged chances in the second extra period -- De Gea thwarting substitute Dwight Gayle with his feet, Carrick heading wide -- before United academy graduate Lingard, a 90th-minute replacement for Mata, claimed a piece of FA Cup history.
Antonio Valencia's drilled cross was cleared by Damien Delaney, but the ball popped up for Lingard, who sent a volley whistling into the top-left corner before tearing off his shirt and racing towards the United end in gleeful celebration.