PSG host relegation battling Le Havre on Saturday
A few days after beating Premier League champions Liverpool, Arsenal gave another gritty and disciplined display to set up a final against Manchester United or Chelsea, who meet on Sunday.
City dominated the early exchanges, pinning Arsenal back, but were stopped in their tracks when Aubameyang produced a neat finish in the 19th minute following a flowing end-to-end move.
Arsenal soaked up desperate City pressure in the final stages but never looked like being opened up as they ended a miserable run of seven successive defeats against Guardiola's City, including a 3-0 away league defeat a month ago.
Mikel Arteta's Arsenal side are now one win from securing a record-extending 14th FA Cup title for the north Londoners.