Lacazette fires Lyon into French Cup final
Valenciennes, who are almost certain to be relegated from Ligue 2, had a first-half goal disallowed following a VAR review for a foul in the build-up.
Former Arsenal attacker Lacazette won and converted a penalty in the 51st minute and then added a second with a clinical finish on the turn.
Gift Orban replaced Lacazette and tapped in Lyon's third with 15 minutes left to seal Lyon's place in the May 25 final in Lille.
It will be Lyon's first appearance in the final since 2012, when they beat third-division Quevilly to lift the most recent of their five French Cups.
Record 14-time winners PSG host Rennes on Wednesday in the second semi-final.