The Togo international has arrived at Molineux on a four-year contract, and becomes new boss Stale Solbakken's sixth summer signing as the club look to win promotion back to the Premier League.
Wolves were believed to be in the market for a winger after the sale of Matt Jarvis to West Ham last week for a fee in the region of £10 million.
"I am so very happy to sign for Wolves," Boukari told the club's official website. "It will be a pleasure for me to play for the club and for the fans.
"I know it is not the Premier League but that is not a problem because I just want to play football and hopefully I can do that at Wolves.
"I want to contribute and score goals and help the team do well. – and we want to aim for promotion.
"I know there is pressure and fans wanting us to do well but that is good and I will enjoy it."
Boss Solbakken added: "I am delighted to have signed Razak.
"He is a winger with good speed who can play on both sides and give us more options in the wide areas.
"We have been aware of him and know he has played a lot of games for Rennes and had some good seasons.
"He had an injury last season but is fit now and ready to go and he will help us in what we are trying to do."