The Frenchman, 59, takes over for Luciano Spalletti, who left the team in May after leading Napoli to their first Scudetto in 33 years in order to take a break.
Garcia won the French league and cup with Lille in 2010–11 while managing Roma in Serie A, just like Spalletti did.
“I have the pleasure of announcing that after having a meeting with him during the last 10 days, Mr Rudi Garcia will be the new coach of Napoli,” said owner Aurelio De Laurentiis.
“A sincere welcome to him and a big good luck!”
Garcia left his most recent position at Al Nassr in Saudi Arabia in April after stints at Marseille and Lyon respectively.