A statement on the official website confirmed that the 29-year-old has moved across London to join West Ham, ending his two years on the Gunners’ books.
Signed from Deportivo La Coruna in 2016, Perez struggled for first-team opportunities during his debut campaign under Arsene Wenger and returned to the Spanish side on loan last season – suffering relegation to the second-tier.
Perez did catch the eye in flashes during his spell in north London, scoring a stunning volley against Bournemouth and a hat-trick in a Champions League clash against FC Basel.
He leaves after netting seven times in 21 appearances, with new boss Unai Emery deciding the versatile attacker was surplus to requirements ahead of his debut campaign.
Arsenal could see a number of further departures today, with Danny Welbeck and David Ospina both tipped for an exit.