It was her second US Open title and third Grand Slam title after her victories at the 2018 US Open and 2019 Australian Open.
"In the end, all I focus on is what I can control on the tennis court. That's what I did in 2018 final. I feel like that's what I did this time," said the 22-year-old who defeated Serena Williams to win the 2018 title, reports Xinhua.
Azarenka, 31, stormed to win the first set 6-1 in just 26 minutes while Osaka was uncharacteristically sloppy hitting a whopping 13 unforced errors.
At the start of the second set, Azarenka broke again for a 2-0 lead, but from there Osaka fought back to break her opponent's serve twice and took a 4-3 lead. Osaka then gained the momentum and broke a third time to take the match to a deciding set.
A quarter-century had passed since a woman who lost the first set of a US Open final wound up winning: In 1994, Arantxa Sanchez Vicario did it against Steffi Graf.
"I think in the first set I was so nervous, I wasn't moving my feet. I felt like I was not playing to my best. There are too many things in my head. It would be very embarrassing to lose this in under an hour so I just have to try my best," Osaka said of the turnaround.
Osaka broke in the fourth game of the third set to take a comfortable 3-1 lead. In the next game, Azarenka blew a golden opportunity to get back into the match, wasting all three break points as Osaka recovered from 0-40 down to hold for a 4-1 lead.
After that, Osaka dominated and claimed the set 6-3.
With the runner-up finish, Azarenka said she's proud of herself.
"I haven't had such results in quite a long time, so I'm very excited for it. Today, it's a loss, but it doesn't change for me much. Of course I would have loved to win today. It is what it is," Azarenka said.
"I gave everything that I could today on the court. I felt that I progressed a lot. I've played a lot of great matches. I felt that I've tested myself physically, mentally on very difficult stages. It's been great. I want to continue to keep going the same way, enjoy myself," she added.
Also read: Kid's night: Osaka, 20, beats her idol Serena to win US Open