The former Chelsea interim boss signed a two-year deal and will replace Walter Mazzarri, who has moved to Inter Milan.
When Alan Pardew's job was on the line last week, Benitez topped a fans' poll as the man Newcastle fans thought they had a realistic chance of tempting to St James' Park.
But the speculation is all 'pie in the sky' now ... because we aint gonna get him.
Benitez paid tribute to the Napoli fans after he was confirmed as the club's new manager.
Benitez led the Blues to third place in the Barclays Premier League and won the Europa League after he was appointed manager in November, following the sacking of Roberto Di Matteo.
Despite his success, the Spaniard struggled to win over a section of the Chelsea supporters during his time in charge at Stamford Bridge.
Benitez is hopeful of a better relationship with the Napoli fans and is confident of bringing further success to a side who were second last season - their best finish in Serie A since winning the Scudetto in 1990.
Rafael Benitez: "Now that the agreement is confirmed, I can say I am very happy and very satisfied for having committed to a great club with an illustrious heritage like Napoli.
"I understand the history of the city and how the club forms a fundamental part of the culture and traditions of Naples.
"I must confess that I am extremely excited because I can share my passion for football with the fans of Napoli; it is proven that they are very, very special.
"I look forward to experiencing each and every one of the fans of Napoli and their strong support for this project that we will begin.
"I'm happy to become a member of that great family of Naples and thus we can share the triumphs together. We will begin from the start as we mean to go on and we will fight from the beginning to achieve success for the fans of SSC Napoli."
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