Christophe Galtier's side won 2-1 at Angers to ensure it finished 2020-2021 in top spot, with PSG's 2-0 victory at Brest proving academic.
It is Lille's fourth top-flight title in the professional era and its first since 2010-2011, when Eden Hazard was named the competition's player of the year.
Lille's points tally of 83 is the best in its history and it only lost three matches all season, the last of which was in March against Nimes.
It is Galtier's first Ligue 1 title as a manager, while the match is expected to be his last at the club before he takes charge of Nice.
Lille's triumph was inspired by the form of 35 year-old striker Burak Yilmaz, who scored 16 times in his first campaign in France's top tier.
He is the first player to score at least 15 goals in his first Ligue 1 season with Lille since Moussa Sow hit 25 in their title-winning campaign a decade ago.
It is only the second time in nine seasons that PSG have not been crowned champions, with Monaco also having lifted the trophy back in 2016-17.