Neither club have made an official announcement regarding the Cameroon international and the only confirmation of the transfer has been given by the player himself.
"I am very happy to join Fenerbahce," Bienvenu said on his official website. "This is a great club and I am happy to play for this team. The club have very good players and I hope we will make a great season.
"Thank you for all your messages. I leave Cameroon tonight [Monday evening] and I will be in Istanbul tomorrow [Tuesday]."
The 23-year-old's arrival comes as an important addition to Fenerbahce's attack, an area that was in need of reinforcement following the departures of Dani Guiza and Emmanuel Emenike.