Erling Haaland and Phil Foden both scored hat-tricks, with City running out 6-3 winners in front of a packed Etihad crowd.
The champions were 4-0 ahead at half-time after two goals apiece from Foden and Haaland, as United struggled to cope with the speed of of our football.
Antony got one back for the visitors early in the second half with a fine curling effort.
But Haaland and Foden completed their trebles to put City 6-1 up, before Anthony Martial's close-range header and late penalty reduced the deficit.
It was yet another historic day at the Etihad that will live long in the memory of those in attendance.
Watch highlights of the game above!
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