The 53-year-old will leave his post as Chelsea interim boss and return to Italy where he spent six, largely unhappy, months managing Inter Milan in 2010.
Benitez’s reputation has been restored since his spell at the San Siro, after guiding Chelsea to victory in the Europa League final and a third place finish in the Premier League, which secured qualification to next season’s Champions League competition.
And the Spanish boss will succeed Walter Mazzarri, who was appointed Inter manager last week.
“Rafa Benitez is the new coach of Napoli,” De Laurentiis confirmed on Twitter, also posting a picture of the pair shaking hands.
He continued: “A man of great international experience. A leader.”
Real Madrid boss Jose Mourinho remains the odds-on favourite to become the new Chelsea manager.
The 50-year-old Portuguese coach, who was at Wembley to watch yesterday’s Championship play-off final, has previously confirmed he will leave the Bernabeu at the end of the season.