Former Liverpool, Inter Milan and Chelsea manager will start work at Italian Serie A club in July.
New manager Rafa Benitez excited to start Napoli 'project'
Benitez led the Blues to third place in the English 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.
"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," he said on his official website, www.rafabenitez.com. "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."
Benitez also confirmed that fitness coach Francisco de Miguel Moreno and goalkeeping coach Vicente Javier Valero Berchili, who were both part of his backroom team at Liverpool, Inter Milan and Chelsea will join him once again.
Benitez will begin his new job in July and Napoli were delighted with their acquisition.
"Rafa Benitez is the new coach of Napoli," read a statement on www.sscnapoli.it.
"The agreement was signed today in London.
"SSC Napoli is happy to welcome a coach so prestigious in their own family. A welcome also to his collaborators."
The news was first broken by club president Aurelio de Laurentiis, who announced the signing on his verified Twitter feed.
De Laurentiis posted a picture of himself shaking hands with Benitez, and wrote: "Rafa Benitez is the new coach of Napoli. A great man with international experience. A leader."
The appointment ends the mounting speculation over the 53 year old's future after he was linked with the vacancies at Real Madrid and Stoke City.
Mazzarri, who guided Napoli to the Coppa Italia in 2012, resigned from the Serie A runners-up last Sunday night and was confirmed as the new Inter Milan coach on Friday.
This is not the first time Benitez has followed a successful manager in Italy. He moved to the San Siro the summer after Jose Mourinho had guided Inter to the Champions League and will be met with lofty expectations in Naples.
His first job will be attempting to keep hold of star player Edinson Cavani, who has been heavily linked with a move away from Italy this summer.
Benitez's finest hour came in 2005 when he won the Uefa Champions League with Liverpool and this month's Europa League triumph followed success in its predecessor, the Uefa Cup, with Valencia in 2004 before his move to Anfield.
He also won the Spanish Primera Liga twice with Los Che and has won the English and Italian domestic cups with the Reds and Inter.