Russian Pavlyuchenkova, who entered the WTA Premier event unseeded, came from behind to beat Italian Sara Errani 3-6 6-2 6-3 in the decider.
She defeated top seed Maria Sharapova in three sets on Saturday to book her place in the final and her victory capped off an excellent tournament.
The 22-year-old had beaten seventh seed Carla Suarez Navarro and fourth seed Angelique Kerber earlier in the hard-court event before causing another upset on the final day in the French capital.
Pavlyuchenkova struggled on serve during the first set, allowing third seed Errani to take control.
The loser made two breaks and claimed the early momentum but the world number 26 responded strongly, with three breaks of her own setting up a third and final set.
Errani, who won her way through to the final with a gutsy three-set win over Alize Cornet that lasted more than three hours, ran out of energy in the latter stages, allowing Pavlyuchenkova to take advantage as she sealed her maiden WTA crown with another comeback win.