The 29-year-old Boutier finished at 14-under 270 overall. She is the first Frenchwoman to win the tournament, which became a major in 2013.
“It has been my biggest dream since I started watching golf,” Boutier said. “This tournament has always been very special to me, even just watching as a teenager and just to be able to hold this trophy is pretty unbelievable.”
Boutier, who had never finished better than 29th in six previous appearances at the tournament, was six shots clear of second-place Brooke Henderson of Canada, who was eight-under after her final round of 70. Kiwi Lydia Ko finished in a share of 61st at six-over.
Boutier took a four-shot lead into the final round and eased any worries she may have had with two birdies to start and another on the fifth hole.