The 24-year-old arrives as Les Dogues strengthen their defence following the departures of Aissa Mandi and Chancel Mbemba.
“The overwhelming emotion today is pure joy. I'm incredibly happy to have had this opportunity to sign with LOSC, which I believe is the ideal club for the next stage of my career and offers the perfect environment to develop,” Nianzou told club media.
“The most important thing for me is to regain my full confidence, my smile, playing time, and thus be able to help the team win. My discussions with the president have always been very clear.
“He told me upon my arrival that we work differently here; I'm here, too, to bring my own unique perspective.
“I'm also happy to be back in France, the country where I was born and where I learned to play football. I'm really looking forward to meeting my teammates and the fans. I'm a Dogues too now”
Despite an injury-plagued career that has limited him to 103 senior appearances for Paris Saint-Germain, Bayern Munich and Sevilla, Lille hope the former France youth international can revive his career after returning to Ligue 1.