Ostapenko, who is the reigning French Open Champion came into the match without having dropped a set or lost a tiebreak during the entire Miami finals, but both run came to an end in her encounter with Stephens.
On her way to the final, Stephens knocked off No. 3 seed Garbine Muguruza (6-3, 6-4) in the round of 16 and No. 10 seed Angelique Kerber (6-1, 6-2) in the quarterfinals-not to mention former world No. 1 Victoria Azarenka (3-6, 6-2, 6-1) in the semifinals.
I think coming back to play tennis, I feel so good that I'm able to compete every week. But if the winners number approaches the errors number, Ostapenko is in her comfort zone.
Ostapenko has now won both of her meetings against Svitolina, included a victory over the 23-year-old at Wimbledon last year. "When she was hitting great shots, I just accepted that some good shots were going to be hit and just didn't harp on it too much".
"I knew that I was just going to have to run a lot of balls down".
The crowd favourite had just six winners, compared with 25 for Ostapenko, but 48 unforced errors by the Latvian and Stephens' relentless defence were the difference.
The 20-year-old Ostapenko, now at career-high No. 5 ranking, was No. 64 entering last year's Miami Open.
"This place is pretty special to me".
Can Stephens learn to win when she does have expectations of success? "I'm sure it will be attractive". After Stephens' strong forehand victor to go up 6-2, Ostapenko nearly pulled even before faltering in the 57-minute first set.
Adding to her triumphant weekend, Stephens, who was seeded only 13th in Miami, will make her world top-10 debut on Monday, after rising to number nine.
It's something that I have wanted for a really long time. "Hopefully I can make some dents there, as well, during the clay court season".
In the second set Ostapenko got an early break but it would be her only game as Stephens steamrolled to the title. 'I was thinking that my life was over because the only thing I had was tennis and that was the only thing that I knew, ' Stephens admitted.
It's something I really look forward to.
"Even when I am down or people are doubting me, there are so many great opportunities out there I didn't worry".