The 26-year-old winger, who has spent the past two seasons at the Eredivisie outfit, has agreed a five-year deal to become Rafa Benitez’s first signing of the summer
The Belgium international has been capped 19 times, and will become Rafael Benitez’s first signing since being appointed as the Partenopei boss.
The playmaker scored 16 goals and created a further 17 in the Eredivisie this season and is excited to take the next step in his career.
“Rafael Benitez wanted me really badly and that gives me a lot of confidence. And when people doubt me and say Serie A is different from the Eredivisie because I won’t play against any Dutch defenders, that is when I’ll be at my best,” he told De Telegraaf.
Mertens spent the past two seasons with PSV, scoring 37 goals in 62 appearances.
Napoli president Aurelio De Laurentiis confirmed the signing through his Twitter feed.
“I am happy to tell you that a few minutes ago I closed the deal with PSV for Dries Mertens," he tweeted.
“In the last few days Dries has been in Naples. He told me that he fell in love with our city, with its greatness. Welcome Dries!”