Lyon had dominated the top tier of women's football in France, its stranglehold on the league dating back to 2007.
PSG had finished second on eight occasions during that period, but that changed thanks to a 3-0 home win over Dijon in its final game of the season.
French capital club PSG went into the final round a point clear atop the table after its goalless draw away to rival Lyon in the penultimate fixture.
PSG got its hands on the trophy thanks to goals from Sara Dabritz, captain Irene Paredes and Jordyn Huitema, despite Lyon's 8-0 demolition of Fleury 91.
Olivier Echouafni's PSG went through the league campaign undefeated after 22 games, winning 20 matches, while scoring 83 goals and conceding just four times.
It is not the first time PSG has snapped a Lyon streak in 2020-2021.
Lyon suffered its first Division 1 Feminine loss in four years, the club's incredible streak halted by PSG in November.
The dominant force of women's football in France and Europe, Lyon's 80-match unbeaten league run – which featured 75 wins – was ended after a 1-0 loss.
Not since December 2016 had Lyon tasted league defeat.
PSG also upstaged Lyon after extra-time in the Women's UEFA Champions League quarter-finals this season.