Naomi Osaka

Japan's Osaka, 24, was beaten 4-6 6-3 7-6 (10-5) at Melbourne Park.

Unseeded Anisimova, 20, will play Australian top seed Ashleigh Barty in the last 16.

Barty has still not dropped a set this week after a 6-2 6-3 victory over Italy's Camila Giorgi.

The 25-year-old Queenslander is carrying the hopes of a nation desperate to see a home Australian Open champion for the first time since Chris O'Neil in 1978.

Most expected Barty to face Osaka in the last 16 when the draw pitted two of the game's biggest stars in the same section.

Japanese fourth seed Osaka, 22, won 1-6 6-3 6-3 for her second US Open title.

Osaka was overwhelmed in the first set and was in danger of trailing 3-0 in the second before recovering to win 10 of the next 11 games to take momentum.

Belarusian Azarenka, in her first major final since 2013, was broken for 5-3 in the decider before Osaka served out.

Osaka shrieked with joy as she took her second match point, then calmly lay on the court and stared at the New York sky as she contemplated her latest achievement.

Osaka triumphed 6-2 6-4 on Saturday in a final that was overshadowed by a dispute between opponent Serena Williams and umpire Carlos Ramos.

Williams was issued a code violation for what the official deemed to be coaching from Patrick Mouratoglou, irritating the 23-time major champion who insisted she was not a cheat.

A point penalty for racquet abuse led to her branding Ramos a "liar" and a "thief" and she was then docked a game, after which the American called for the match referee and alleged she was being treated differently to male players.