The 18-year-old midfielder has signed a temporary deal with the French club and could now compete in next season's Champions League
The 18-year-old made four appearances for the Premier League champions last season and was named man-of-the-match during City's Capital One Cup win over West Ham.
Lopes will now look to gain more first-team experience in Ligue 1 and could compete in the Champions League, with Lille having finished third in the 2013-14 season.
Upon completing his move, he said: “I feel very happy to have signed because it is a new step in my career and it is a good opportunity for me to develop as a player. I hope to get much stronger next season, and I’m really looking forward to getting started.
“It is very important for me to play in a professional league for the first time, and it is important for me to experience what it is like to play in that environment.
“It is very different to what I have played in before, but I watched some of the games last year and I think it will be a good league for my development.”
Manchester City elite development squad boss Patrick Vieira also hailed the move, insisting Lopes will be given a chance to shine in France.
“Marcos is joining a league that is very demanding physically, but is very good at developing young players. It is great that he has the chance to take his next step in a very strong league that will be challenging for him," the former France international added.
“I know the manager at Lille, Rene Girard, and he is very detailed in his approach and is keen to give young players a chance.
“He may also have the chance to play in Europe, which would be a fantastic experience for Marcos, and will help him grow up as a player. They are a very young group at Lille, so it is a good opportunity for him to show what he can do."