Naomi Osaka won the US Open after an angry Serena Williams accused the umpire of being a "thief" in some of the most dramatic scenes at a Grand Slam final.

Williams was given a game penalty for her outburst, which followed racquet smashing and another code violation as Osaka won 6-2 6-4 in New York.

Osaka, 20, kept her focus to become the first Japanese to win a Grand Slam.

Williams refused to shake hands with umpire Carlos Ramos after the match.

The American, 36, graciously congratulated Osaka at the net after the 20th seed completed an extraordinary victory and, although Williams' behaviour will grab the attention, nothing should detract from a classy and composed display from Osaka at Flushing Meadows.

"I'm sorry it had to end like this," a crying Osaka said.

Naomi Osaka was left hiding her tears at the presentation ceremony of her first Grand Slam trophy