She became Asia's first world No. 1 ranked player with the 7-6 (2), 5-7, 6-4 victory over Petra Kvitova. The match lasted 2:27 at Rod Laver Arena.
The 21-year-old went up 1-0 in the first set and had to hold off her Czech counterpart after a 6-6 tie break in the set. Kvitova came back strong in the second set, going up 2-0 before Osaka jumped up 4-2. Osaka held a 5-3 lead in the set before Pvitova won the next four points to take the set.
"I just felt like I didn't want to have any regrets," Osaka told reporters. "I think that if I didn't regroup after the second set, I would have looked back on this match and probably cried or something."
Osaka regrouped in a big way. She fell down 1-0 in the first set before winning the next three points. Pvitova climbed back in with a 104 mph ace to make it 3-2, but Osaka was able to hold her off down the stretch to win her second career Grand Slam.
"For me it hasn't really sunk in," Osaka said of being No. 1. "Maybe in the next tournament that I play, if I see the No. 1 next to my name, I'll feel something. But for now, I'm more happy that I won this trophy."