Boufal signed a four-and-a-half year deal with Rene Girard's side, bringing an end to months of speculation about his future.
The 21-year-old has lit up the second division this season with Angers with his performances attracting interest from the likes of Milan, Juventus and Newcastle United.
An attacking midfielder who has drawn comparisons to Zinedine Zidane and Javier Pastore, Boufal scored four goals in 16 Ligue 2 appearances this season and he couldn't be happier with the opportunity to play first division football.
"Above all, I feel joy. I am very happy to play at a new level," Boufal told Lille's official website.
"The environment here is ideal for work and progress."
Lille, who finished third in Ligue 1 last season, have struggled for consistency in their current campaign and find themselves in 11th place as a result.
Boufal should give Lille another option going forward in a season where they have struggled for goals, and he is confident he can cope with the jump in quality from Ligue 2 to the top flight.
"Ligue 2 allowed me to toughen up, especially physically. I will cross another level with Ligue 1, both physically and technically," he said.
"I feel no negative apprehension. The requirements will not be the same as at Angers [but] I'm not worried about much.
"There is a very good coach and a high-level group here. I hope to be able to show my qualities and gain the confidence of the coach."
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