Perez, 27, has been officially unveiled by the Gunners after the London club triggered the player's £17-million release clause late last week.
And, after successfully completing a medical in London this week, the player has officially become manager Arsene Wenger's second big acquisition of the transfer window.
"He's not only a goalscorer, he's a guy who combines well with partners, who can give a final ball and makes good runs," Wenger told Arsenal's official website.
"He's got a good eye for goal and had an outstanding season last year."
Perez joined Deportivo on a permanent deal last year from Greek side PAOK, following a successful loan spell at Estadio Riazor.
He went on to enjoy a hugely successful 2015/16 campaign, scoring 17 times in 36 La Liga appearances.