Halep battled back in the next game, holding two set points from Stephens, to set up a tiebreak. Stephens, the reigning U.S. Open champion, is now 0-8 in matches against No. 1-ranked players.
"I think the match was a very good level of tennis even if the rhythm was a little bit mixed".
"Obviously I'm sad I lost, but losing to the number one player isn't too bad".
Halep, quoted on the WTA website, added: "I just want to give my best tomorrow and to enjoy the final because it's a great thing after a long break to play final at a big tournament". I thought she played well.
Stephens rallied to within 5-4 before Halep, on her fourth match point, slammed her third ace of the match and dropped to her knees in triumph.
"It was really tricky conditions.and we were both struggling a little", Barty said in her on-court interview. She doesn't give up that much now.
"It's just getting confidence and playing good tennis", Stephens said.
She broke two of Stephens' serves to take a 4-1 lead.
She eventually managed to break the American in the seventh, but Stephens replied with her own and ultimately closed out the match 6-3 6-3.
Halep outlasts Stephens in 3-set thriller to win Rogers Cup
It was Halep who drew first blood in the decider, but Stephens, looking the fresher of the two, pegged her back at 2-2.
Stephens again looked to be on the brink of the first set after surging into a 5-1 lead which soon became 6-4 in the tiebreak.
Stephens refused to go quietly though, saving a match point before breaking for 5-3, and then saving two more match points to hold.
Spaniard Carolina Garcia, the No.6 seed, was combative in the first set before Halep secured a crucial break to win the opener 7-5.
But Halep couldn't hold her serve in the ninth game of the second set.
She broke back for 2-2, but then suffered a letdown as Halep broke service twice more to take the lead.
However, Halep called on all her reserves of energy to break the resilience of the third seed, shrugging off a double fault at championship point along the way, as she completed a memorable victory.
"I hit some dropshots, which I don't normally do, because I was too exhausted", said Halep, who has reached at least the semifinals in four straight Rogers Cups. "I hope in the future it's going to be better".
Former Tesla engineering chief returns to Apple
Apple spokesperson Tom Neumayr confirmed that Field had returned to the company but did not reveal what project he was working on. John Gruber , an Apple expert who writes the Daring Fireball blog , said Field was "a seemingly ideal fit" for Apple .