WATCH: 'I'm not a cheater' - Serena Williams in extraordinary on-court meltdown as she loses US Open final
Naomi Osaka won her first grand slam title as Serena Williams suffered an extraordinary meltdown in the US Open final.
The headlines were supposed to be about Williams' bid for a record-equalling 24th grand slam title and Osaka trying to become Japan's first slam winner, but instead an argument with umpire Carlos Ramos that escalated dominated the match.
Williams was furious when she was given a coaching violation early in the second set after a hand gesture from her coach Patrick Mouratoglou.
She was then docked a point for a second violation when she smashed her racket after dropping serve at 3-3. Continuing her argument with Ramos at the change of ends, Williams accused him of being a thief for taking a point away from her.
Ramos gave her a third violation, which resulted in a game penalty, putting Osaka 5-3 ahead. A tearful Williams argued her case with tournament officials but, although she held serve in the next game, Osaka served out the victory 6-2 6-4.
What a baptism this was at the highest level for the 20-year-old, who was giving away 30 grand slam finals and 16 years of experience but was the one who kept her cool.
Williams was initially rattled in the first set by the quality of play from Osaka, who seemed to have no problem dealing with opponent's power and had the sharper movement and serve.
Serena Williams after getting penalized because she called judge a "thief" "There;s a a lot of men who have said things and because they are men nothing happens to them"....pic.twitter.com/Vr9WTspqFw— gifdsports (@gifdsports) September 8, 2018
While all the drama happened around her, Osaka somehow maintained her composure, sitting at the final change of ends with a towel over her head to block everything out.
Neither Williams nor her vocal fans initially realised she had been given either the point or game penalty, and the boos and jeers on the second occasion were deafening.
The capacity Arthur Ashe crowd had arrived hoping to witness Williams make much more positive headlines by equalling Margaret Court's all-time record of 24 grand slam singles titles.
After Osaka hit the final serve, Williams warmly embraced her young opponent, who grew up idolising the American, then refused to shake Ramos' hands, instead giving him a final verbal volley.
It is not the first time the 36-year-old has run into trouble with officials at Flushing Meadows. In a semi-final against Kim Clijsters in 2009, she was penalised for threatening a line judge and fined.
Two years later, during a final loss to Sam Stosur, Williams called umpire Eva Asderaki "a hater" and "unattractive inside" for calling a hindrance penalty against her.
The presentation ceremony began with more booing from the crowd before a tearful Williams said, to wild cheers: "I don't want to be rude. I don't want to do questions.
"I just want to tell you guys she played well. Let's make this the best moment we can and get through it and give credit where credit is due. No more booing. Let's be positive."
Osaka was also in tears, and said: "I know everyone was cheering for her and I'm sorry it had to end like this. I just want to say thank you for watching the match.
"It was always my dream to play Serena in the US Open finals. I'm really glad I was able to do that."