Chilean striker Alexis Sanchez's scrambled extra-time winner secured Arsenal an FA Cup final date with Antonio Conte side Chelsea - and ensured Manchester City boss Pep Guardiola will end a season without a title for the first time in his coaching career.
The Gunners striker [Sanchez] settled a contentious semi-final 11 minutes into the extra period after Manchester City failed to clear playmaker Mesut Ozil's free-kick.
Arsenal showed great resilience to come from behind - and eased the pressure on coach Arsene Wenger - after forward Sergio Aguero raced clear of left-back Nacho Monreal to put Manchester City ahead in the 62nd minute.
The Spain International made amends with the equaliser 11 minutes later as he drilled in midfielder Alex Oxlade-Chamberlain's cross at the far post - but the Pep Guardiola side were left nursing a serious sense of injustice after this disappointing defeat.
They had a goal wrongly ruled out in the first half when winger Leroy Sane's cross was considered to have gone out before Aguero and midfielder Raheem Sterling combined to turn it into the net, while playmakers Yaya Toure and Fernandinho hit the woodwork after the break.
It left Gunners victorious and Arsene Wenger aiming for a record seventh FA Cup joy.