The 28-year-old striker signs a five-year deal with the club and becomes the most expensive forward in the history of football.
Juventus confirmed the news on Twitter and on their official website.
The official tweet read:
The club released an official statement which read:
"Juventus Football Club can today confirm that it has purchased the registration rights of Gonzalo Higuain for €90 million, payable in two financial years.
"The player has agreed a five-year contract with the club."
The Argentine will earn £6.3m per year at Juventus. He passed a medical in Madrid on Friday after Juventus agreed to pay the striker's release clause, a record transfer fee for a striker.
Gonzalo Higuain thus becomes the third most expensive player in the history after Gareth (£85m), and Cristiano Ronaldo's (£8om) both paid by Real Madrid in 2013 and 2009 respectively.
Higuain is Juventus's fifth signing of this season after, Dani Alves from Barcelona, Miralem Pjanic from AS Roma, Medhi Benatia from Bayern Munich, Marko Pjaca from Dinamo Zagreb.
The striker had scored 39 goals for Napoli last season in all tournaments and was also the highest goal scorer in the Serie A.