"Tottenham Hotspur is a great club with a strong tradition and fantastic support, both at home and throughout the world," Villas-Boas told the club's official website.
"I feel privileged to be its coach. For me, this is one of the most exciting coaching positions in the Premier League.
Villas-Boas enjoyed a hugely successful season at Porto where he won four trophies before a disappointing spell at Chelsea last season.
The 34-year-old is pleased to have taken over at White Hart Lane and believes any coach would love to work with the existing squad of players at the club.
"I have had several discussions with the chairman and the board and I share their vision for the future progress of the club. This is a squad any coach would love to work with and together I believe we can bring success in the seasons ahead," Villas-Boas said.
The club's chairman, Daniel Levy also revealed his excitement at Villas-Boas appointment, stating: "I am delighted that Andre has agreed to become our new head coach.
"He has an outstanding reputation for his technical knowledge of the game and for creating well-organized teams capable of playing football in an attractive and attacking style," Levy added.
"Andre shares our long-term ambitions and ethos of developing players and nurturing young talent, and he will be able to do so now at a new world class training center."
Spurs have also confirmed two members of Villas-Boas' coaching staff have joined the club - with Jose Mario Rocha becoming their first team fitness coach and Daniel Sousa taking the head of opposition scouting role.
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