"I was delighted to accept the offer to coach Zenit because the club is as ambitious as I am," said Villas-Boas at his first news conference. "I hope to have a lot of success with the team and my first aim is to win the Russian championship.
"I am sure we have what it takes to win our remaining matches and become champions. It is my first time in St Petersburg and I am in awe of just how beautiful the city is.
"Peter The Great built this city. I want to build a football team at Zenit which is as great as the city's founder," the 36-year-old added.
The side from Russia's second city are second in the domestic league, three points behind Lokomotiv Moscow with nine games left.
Villas-Boas said he was pleased with Zenit's display at Borussia Dortmund on Wednesday, a game he watched on television in St Petersburg.
Last season's Russian League runners-up won the second leg 2-1 against Dortmund but were knocked out 5-4 on aggregate in the last-16 of the Champions League.
"It was an excellent result," said Villas-Boas. "I really liked how the team played - they played with passion.
"I hope we can use this passion and the knowledge that the team possesses to go on and win our remaining matches."
The Portuguese praised Italian predecessor Luciano Spalletti who spent more than four years in charge before being sacked last week.
"I would like to thank Luciano Spalletti who has left a great memory here and has written an important chapter in the club's history," said Villas-Boas who was also dismissed in his two previous jobs at Spurs and Chelsea.
He added that Sergey Semak, who was in charge for the second leg against Dortmund, would continue to work at the club as his assistant.
The rest of Villas-Boas's backroom staff will be Portuguese coaches.
"I speak a number of languages," said Zenit's new coach. "I like to learn new ones and I really hope I will be able to learn to speak Russian."
Villas-Boas's first league game in charge will be against sixth from bottom Krylya Sovietov Samara on Monday.
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