Indeed, for Ostapenko, the win represents her first WTA tour title of any sort as a professional. Meanwhile, the result means world No. 4 Halep won't overtake Angelique Kerber as the new world No. 1.
Halep was a break up in the second and third sets, but on both occasions Ostapenko was able to come back strongly.
She made history, per ESPN Stats and Info:
The match was the pair's first meeting. ESPN Tennis analyst Brad Gilbert was intrigued by their contrast in styles ahead of the clash:
That contrast would make itself apparent throughout the contest, somewhat reminiscent of Andy Murray's semi-final clash with Stan Wawrinka on Friday, but both players enjoyed electric starts to the match.
Ostapenko quickly set about showing off her power as she broke Halep in the opening game, though the Romanian hit back immediately.
Eurosport UK were in awe of the 20-year-old's booming forehand:
So was BBC 5 live's David Law:
What let the youngster down was her first serve, and she hit the target with just 48 per cent of them in the opening set, according to the tournament's official website.
Nevertheless, it was not until the final game, with Ostapenko serving to stay in the set at 4-5, that Halep was able to break her again.
The third seed sealed the set when the Latvian sent a forehand long. The New York Times' Ben Rothenberg compared the results of her high-risk, high-reward offensive play with Halep's more measured and consistent defence:
Ostapenko's approach would prove costly early in the second set as she gave away an early break, while several unforced errors in the games either side prevented her from capitalising on three break points of her own.
Tennis writer Courtney Nguyen thought they were as much a product of Halep's imperious defending as anything else:
The world No. 47 was eventually able to stop the rot—saving three break points in the process—and then broke back on the way to levelling the scores at 3-3:
With the momentum fully behind her, Ostapenko powered to the second set with two more breaks of Halep, despite her experienced opponent pulling one back herself.
The 25-year-old took a 3-1 lead early in the third as she showed renewed focus, but the resilient Ostapenko fought back once again with some sublime play and yet more blistering winners.
Before long, she was on the verge of glory. She won the championship point in some style with an incredible return:
The quick grass surface at Wimbledon should suit Ostapenko well, so it will be intriguing to see how she fares when the Slam comes around in short order.
As for Halep, she will need to recover from her second major final defeat.