In a week of improbable European comebacks, Valencia, trailing 3-1 from the first leg, were seeking to become the latest side to overturn a hefty deficit.
Valencia made the perfect start as Kevin Gameiro slid in to convert Rodrigo’s centre with 11 minutes played.
Arsenal hit back almost immediately when Aubameyang notched his first of the night with a fine finish from outside the box from Lacazette’s flick on.
Valencia continued to push forward, but were caught napping by Lacazette’s curling effort just after the break to put the visitors ahead on the night.
Gameiro converted Rodrigo’s mis-hit shot just before the hour to set up a possible grandstand finish.
But Aubameyang soon restored Arsenal’s lead before completing his treble two minutes from time to book their first European final since they lost the 2006 Champions League final to Barcelona.
The News Agency of Nigeria (NAN) reports that Arsenal will face Chelsea in an all English final in Baku, Azerbaijan on May 29 after it beat Eintracht Frankfurt on penalties after a 1-1 draw in regulation time.