Tenth seed Stephens, the first American not called Williams to reach the Roland Garros final since Jennifer Capriati in 2001, by contrast has a flawless record in Grand Slam finals having beaten friend Madison Keys to win last year's U.S. Open.
And once the Romanian levelled the match at one set apiece, she never looked back, racing through the decider to the delight of a pro-Halep crowd.
"Thanks guys it was incredible and I felt your support", Halep, twice a runner-up in Paris before Saturday, told the crowd who were chanting her name. The Spaniard won the French Open in 2016 and Wimbledon a year ago. I just didn't give up.
Simona Halep is healthy at this Final and longs to catch a break and get a title here at Roland Garros.
Where can you follow the Simona Halep vs Sloane Stephens French Open women's singles final online? However, despite how well Halep has played up to this point, she has a lot of showing and proving to do, as she's developed a history of choking in final appearances.
"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.
Stephens broke for 3-1 and looked in control against a more anxious opponent who had started to put ore air under her shots with some moonballs. Stephens scored her first Grand Slam title at the US Open in September 2017 in NY. "There's no-one I'd rather lose to than the number one in the world so congratulations to you and your team", she added.
Halep drew on the memories of her unpleasant experiences in a 2014 French Open final defeat to Maria Sharapova, a showdown with Jelena Ostapenko previous year and her Australian Open loss to Caroline Woznacki in January to pull herself off the ropes.
A year ago Stephens, 25, could hardly have imagined contesting Grand Slam finals - let alone having won one already by the time she turned up in Paris this year. She showed she had learned from her two losses, especially the loss in 2017 to Jelena Ostapenko after leading by a set and 3-0 in the second. "I just have to start to relax and enjoy the match".
Halep became just the second Romanian woman to win a grand slam.
"I was dreaming about this moment since I started to play tennis. I wish in the future to play more finals here, because it's a really attractive tournament and it is my favourite one".
In the opening set, Stephens' sharp movement across the baseline enabled her to return everything Halep threw at her, while forcing the Romanian into errors and hitting some wonderful winners herself.
While Halep sometimes has trouble with so much on the line, Stephens has been flawless in title matches, going 6-0.
Halep celebrated her victory in a way usually seen at Wimbledon, climbing into her box to greet friends and family.
The script was different on Saturday at Roland Garros as Halep rallied past Sloane Stephens and did not crumble in the end.
Russian tennis player Elena Vesnina praises Halep. Stephens indicated to Halep she should raise it proudly overhead.