Manchester City players celebrate winning the English FA Cup final soccer match between Manchester City and Manchester United at Wembley Stadium in London, Saturday, June 3, 2023. Photo: AP
Pep Guardiola's men completed a domestic double at Wembley and can become just the second side, after United in 1998/99, to win the Premier League, FA Cup and Champions League in the same season should they beat Inter Milan to become European champions for the first time on June 10.
Gundogan scored the fastest goal in FA Cup final history after just 12 seconds.
United levelled on 33 minutes through Bruno Fernandes' penalty after Jack Grealish was harshly penalised for handball.
But the City captain, in what could be his final game for the club on English soil, volleyed home the winner six minutes into the second-half.
The first ever major final between the Manchester giants had the most explosive of starts.
Most of the 83,000 crowd were still taking their seats from the pre-match festivities when Victor Lindelof's headed clearance sat up perfectly for Gundogan to volley home a stunning strike after just 12 seconds.
That appeared to set the tone for the Premier League champions.
Rodri headed into the side-netting moments later before Erling Haaland failed to get a clean connection on Gundogan's enticing cross.
United were barely able to get across the halfway line in the first half hour, but got the break they needed to get back into the game.
Aaron Wan-Bissaka's header back across the City box brushed the arm of Grealish and referee Paul Tierney was instructed to review the incident by VAR.
Despite City's protestations, Tierney pointed to the spot and Fernandes coolly sent Stefan Ortega the wrong way.
The Portuguese's celebrations in front of the City fans were met with a flurry of objects thrown from the stands, one of which struck Lindelof.
City boss Pep Guardiola was also showing his fury at the officiating as VAR did not intervene seven minutes before half-time when Kevin De Bruyne was wiped out by Fred inside the area and no penalty was awarded.
De Gea question mark
At the other end, United passed up a great chance to turn the game around before half-time when Raphael Varane fired high and wide at the back post from a corner.
Having fought so hard to gain a foothold, United were made to pay for another slow start in the second-half.
Gundogan was the goalscorer again as he fired home from De Bruyne's free-kick.
But more questions will be asked of whether David De Gea remains the right man to be United's number one goalkeeper after the 32-year-old Spaniard's sluggish attempt to keep it out.
De Gea did at least make a big save with his legs to deny De Bruyne a third to keep United in the game on the hour mark.
Gundogan thought he had a rare FA Cup final hat-trick 20 minutes from time, but was flagged offside when he turned in the rebound after De Gea denied Haaland his 53rd goal of the season.
United rallied in a tense finale as Marcus Rashford and Alejandro Garnacho flashed efforts inches off target.
The ball came back off the City bar in a goalmouth scramble deep into stoppage time.
However, the Red Devils could not find the goal to deny Guardiola an 11th major trophy as City boss and protect the unique legacy of Alex Ferguson's great side 24 years ago.
Only Inter in Istanbul in a week's time now stand between City and matching the greatest achievement English club football has ever seen.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)