"I am signing for the Champions League winner," Hazard, 21, said on his Twitter feed.
Hazard, named the best Ligue 1 player in the last two seasons, had been expected to join either Premier League champions Manchester City or runners-up Manchester United after he said he would choose between the two.
The gifted playmaker, capped 27 times by Belgium, led Lille to the French title in 2011 and scored 20 goals this season, including a hat-trick in his farewell game, as they finished third to qualify for next season's Champions League play-off.
Hazard made his league debut for Lille as a 16-year-old and quickly had scouts flocking to the club's Metropole stadium. His performances earned the Ligue 1's top prospect award for successive seasons, before he secured the full accolade in the last two campaigns.
