Stephens went a set and a break up-the same position Halep lost from in the French Open final last year-in the contest, but faded as Halep battled back to win 3-6, 6-4, 6-1. Halep is looking for her first career Major title.
"It was incredible and thank you for your support", she told the crowd - most of whom appeared to be backing her - on court Philippe-Chatrier. "In the last game I didn't feel like I could breathe any more and didn't want to repeat a year ago, so I cannot believe it. I dreamed of this moment since I started to play tennis and I can't believe it", she added.
Stephens, who was facing the ignominy of a third-set bagel, managed to get on the board with a hold in the fifth game of the decider, but Halep was not to be denied.
When will the Simona Halep vs Sloane Stephens French Open women's singles final be played?
"Then at the Australian Open where she fought so hard and couldn't quite get across the line".
Stevens netted a service return to bow out.
She reeled off nine straight points to lead 3-2 on serve, then broke for 4-2.
"I obviously feel very sad for her, but at the same time I'm very happy for myself", Wozniacki said after the final in Australia.
"So we will see what is going to happen, but I just want to be smiling on court". When Stephens is keeping the ball in play and aggressive defensively, she's one of the tougher players on tour to beat.
The Romanian knows better than anyone how Grand Slam finals can turn though after her 2017 heartbreak against Ostapenko, and she broke back to love to the delight of the crowd.
After three losses in major finals, maybe Halep was trying to convince herself as much as anyone else she actually could do it.
Prior to Saturday, the victor of the first set had won 43 of the past 46 women's major finals. "Her strong serving and power-hitting seemed a little too intense against Stephens, who had all the answers on Thursday", Becker wrote.
She had every answer for Stephens' power and variety, and sealed the victory with an ace to claim her first-ever Grand Slam title.
"I was playing really well on the baseline and solid", the fourth-seeded Tseng said.
But just as the set was slipping away from Stephens, a series of unforced errors by Halep gifted the break back for 4-4.
After Saturday, Halep joined Martina Navratilova (1978 Wimbledon) and Jelena Ostapenko (2017 French Open) as the only women in the Open era to win their first major title after coming from a set down to win in the title match.
The match was all but ended as Halep clinched the double break in game four after some magnificent defending in one of the points of the match. To Halep's dismay, she sent a backhand into the net.