Having already won the EFL Cup after beating Chelsea on penalties and the Premier League after ousting Liverpool in an epic title race, City headed into Saturday's final knowing that history was awaiting them.
If there were any nerves in the City camp, they were certainly well hidden as Pep Guardiola's side produced a footballing masterclass to sweep aside a sorry Watford outfit.
But how different it all could have been. Watford started the final brightly and their game plan was clear early on: sit back, absorb City pressure and then look to exploit the spaces left by the Citizens' overlapping full-backs through the pace of Gerard Deulofeu.
This approach presented Watford with a guilt-edged chance to open the scoring in the 11th minute; Deulofeu was released down the right after Oleksandr Zinchenko had bombed forward, and he cut the ball back to the supporting Roberto Pereyra on the edge of the box. The Argentinian midfielder took one touch, but by the time he'd looked up, the fearless Ederson had rushed off his line and spread himself big to make the save.
Watford then had a big penalty shout ten minutes later after Vincent Kompany blocked Abdoulaye Doucoure's goalbound effort with his arm, but neither VAR or Kevin Friend felt it merited a spot kick, and from there on out the game was virtually all City.
Guardiola's side started to keep the ball better, and broke the deadlock in the 25th minute as David Silva beat Gomes from the edge of the six-yard box after a clever header from Raheem Sterling had found the Spaniard in space.
City doubled their lead just minutes later to put the game almost out of sight before half-time. Bernardo Silva cut in front the right, and whipped in an inch-perfect ball to the back post, where a stretching Gabriel Jesus was on hand to squeeze home from a tight-angle - despite Sterling's best efforts to steal the goal as the ball was crossing the line.
May 18, 2019
Watford started the second half with a determination not to let the moment pass them by, but this left them wide open on the counter attack and they were quickly punished.
Kevin de Bruyne came off the bench to round Heurelho Gomes and tuck home a third after a flowing City counter, and he then set up Jesus with a perfectly timed through ball to make it four.
City were not done there, however, and once again showed their ruthless streak as Sterling added two more in the last ten minutes. The PFA Young Player of the Year tapped home from Bernardo Silva's low cross before following in his own effort to tap home after an impressive Gomes save.
With goal number six, City equalled the record for the biggest ever FA Cup final victory that Bury had set when they thrashed Derby County 6-0 in 1903, although the Premier League champions really should have made the record their own as John Stones missed a simple chance from inside the area just before full-time.
May 18, 2019
With the defeat, Watford miss out on European football, and it will instead be Wolves and Manchester United who will represent England alongside Arsenal in the Europa League next season (unless Arsenal beat Chelsea to get Champions League football in the Europa League final later this month).
So, City become the first ever team to win all three domestic competitions in one season. Without a doubt, Guardiola has built one of the best sides this country has ever seen - the only thing left for them now to cement their place amongst history's greatest teams is success on the European stage.