Halep has been in fine form so far at Roland Garros and eased past former victor Garbine Muguruza 6-1, 6-4 in the last four - a victory which also ensured she will remain the world number one at the end of the tournament.
"Congratulations to Simona. There is no-one else I'd rather lose to than the number one in the world", Stephens, who will rise to four in the rankings, said.
"I think she's had a tough journey", Stephens said of Halep. Honestly, I could not believe. Stephens is one of the best movers on tour, and while Halep has started to become more aggressive, she certainly can't hit many winners against the American and will have to rely on mistakes from her opponent.
Winner, Simona Halep of Romania (R) and runner up Sloane Stephens of The United States (L) celebrate with their trophies following the ladies singles final during day fourteen of the 2018 French Open at Roland Garros on June 9, 2018 in Paris, France.
The psychology of this final involved Halep desperately wanting to break her duck at the Majors and Stephens having the security of already knowing that she had one in the bank.
Simona Halep had been at the precipice of a Grand Slam.
During the trophy ceremony, Stephens - more experienced in such matters, given her triumph in NY last September - noticed that Halep was casually holding her new silver trophy.
"She just raised her level and started playing better". She was the clear favourite a year ago as well to beat Ostapenko and (somehow) managed to find a way to lose. Stephens started better and led Halep 2-0 but the Romanian managed to win 4 consecutive games and take the lead.
On Thursday, it was more of the same as the 25-year-old capitalised on her friend's big match nerves.
Rain cuts short Nadal fightback, Muguruza crushes Sharapova
The Romanian broke serve six times against a player who made the semi-finals at the Australian Open in January. He went on to break Nadal two more times in the second set before the match had to be stopped due to rain.
In womens' play, Sloane Stephens and Madison Keys were to play for a spot in the French Open final.
Coming into the final, she was determined.
On Saturday, Halep finally broke through, becoming the first Romanian woman to win the French Open in 40 years.
Stephens was unable to repeat her US Open heroics at Roland Garros.
But a first major title had eluded her until now, and she said she "could not breathe" as she closed in on it.
"When I was down a break in the second set", Halep told the crowd afterward, "I thought, 'Everything is gone".
"So I think I have done very well to make the finals of the French Open".
With their Davis Cup captain Yannick Noah watching from the stands, Herbert and Mahut claimed their third Grand Slam title together by defeating Oliver Marach and Mate Pavic 6-2, 7-6 (4) in the final. Halep has been lights out with her return this tournament and has produced a combined 14 breaks in her last two matches. Halep has been on the cusp of winning Slams before, but she has cracked mentally on every occasion, losing all three of her finals in three sets.
Halep beat Stephens the last four times they played each other.