Sabalenka was the pre-match favorite, having received 33 of her earlier 34 matches on the Australian arduous courts.
However Keys, a strong baseliner, is among the few gamers on the WTA Tour who has the weapons to wreck Sabalenka.
A shocking opening set, the place she whacked 11 winners and had a rock-solid first serve, set the platform.
Keys was additionally helped by a nervy begin from Sabalenka, whose unstable second serve returned to bother her.
Two double faults within the opening sport allowed Keys to interrupt, whereas one other arrange a second break level within the fifth sport which Sabalenka handed over with a sliced forehand into the online.
Keys continued to play lights out, thumping clear winners from the again of the courtroom and likewise displaying deft touches.
A bemused Sabalenka might solely smile when Keys pulled out an ice-cold drop-shot on the way in which to holding for 5-1.
Nevertheless, Sabalenka was livid with herself after a fourth double fault handed over one other set level – which Keys took with a backhand winner.
The exasperated Sabalenka, who had been demonstrative all through the 35-minute set, determined she have to go off courtroom to clear her head.
When she returned, there was a momentum shift.
Keys was unable to maintain her earlier degree, together with her winners deteriorating and her first serve missing precision.
Whereas Sabalenka was nonetheless missing fluency – illustrated by an extended forehand that left her dropping her racquet in exasperation – she improved sufficient to dominate the second set.
A good and tense decider didn’t produce a break level till the pivotal twelfth sport.
Keys upped the ante with some deep returning that Sabalenka couldn’t deal with, earlier than sealing victory with a beautiful cross-court forehand winner.