The Portuguese playmaker came to prominence with a starring role for City in last season's Capital One Cup semi-final second leg tie against West Ham, setting up two goals in the 3-0 victory at Upton Park.
He has made four other appearances in cup competitions for the Premier League champions and scored one goal, on his debut against Watford on January 5 2013.
He told mcfc.co.uk: "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.
"It is very important for me to play in a professional league for the first time. I think playing in the French League will be very beneficial because it is a league that is getting bigger, better and stronger every year."
Lille finished third in Ligue 1 last season to qualify for the preliminary stages of the Champions League.
And Lopes added: "It would be very exciting to be able to play Champions League football. It would be such a good experience for me to play in that competition, which everyone recognises as the best in European football."
Meanwhile, midfielder Marvin Martin, 26, has signed a two-year contract extension to keep him at Lille until 2019.