Manchester City were playing their first competitive game without Pep Guardiola as their manager in over 10 years, since Manuel Pellegrini oversaw a 1-1 draw with Swansea in May, 2016.
This was not the result they were hoping for.
Arsenal took the lead after just 23 seconds, doubled their advantage thanks to some static City defending in the 23rd minute and added a third three minutes into the second half.
Their defeat was the biggest in the Community Shield since 2014, when Arsene Wenger's Arsenal also beat Pellegrini's City 3-0.
New manager Enzo Maresca gave £116m signing Elliot Anderson his competitive City debut and started Phil Foden, who had been out of favour under Guardiola last season.
Jack Grealish also came on in the second half for his first City appearance in 15 months.