Serena Williams was fined $10,500 on Sunday by officials at the US Open and could face further sanctions after an investigation was launched into her angry outburst during her semi-final defeat by Kim Clijsters.
It is the biggest fine handed out to a woman player since records started being kept in 1990, according to the International Tennis Federation.
"The maximum permissible on site fine of $10,000 has been levied for unsportsmanlike conduct against Serena Williams for her on court behaviour during the women's semi-final," the tournament referee said in a statement.
"Ms Williams also will be fined $500 for racket abuse which took place at the end of the first set of the same match."
Trailing 4-6 5-6 15-30, Williams launched into a second serve but the lineswoman sitting at the baseline held up her finger to call her on a foot-fault -- meaning the American had served a double-fault to go match point down.
Astounded by the verdict, Williams walked over to the official screaming. She waved her racket ominously in the lineswoman's direction and then shook a ball in her clenched fist as she threatened "to shove it down" her throat.
"I swear to God I'm... going to take this ball and shove it down your... throat, you hear that? I swear to God. You better be glad... glad that I'm not, I swear," Williams told the line-judge in her expletive-laden rant.
Having already received a warning earlier in the match for smashing a racket, Williams was handed an automatic point penalty for a second violation which abruptly ended the match, giving Clijsters a 6-4 7-5 victory.
Some former players felt Williams could have been temporarily banned from the tour because of her actions. Although no such punishment was handed out Sunday, the statement did not rule out further penalties.
"The grand slam rule book also allows for an investigation to be conducted... to determine if the behaviour of Ms Williams warrants consideration as a 'major offence' for which additional penalties can be imposed. This investigation has now begun," the statement added.
Almost 24 hours later, the tirade continued to be headline news in the United States and Roger Federer said it had left a "sour taste for everyone." WTA Tour chief Stacey Allaster deemed Williams's conduct "inappropriate and unprofessional."
"No matter what the circumstances, no player should be allowed to engage in such behaviour without suffering consequences. I have spoken with the USTA about this matter and I agree with the action they have taken," Allaster said in a statement.
"As a role model, it's important for a leader like Serena to step forward and recognize her behavior last night was unacceptable."
The fine handed out to Williams exceeded the penalty imposed on John McEnroe when he was defaulted from a fourth-round match at the 1990 Australian Open.
On Saturday the 27-year-old Williams was unrepentant about her rant but changed her tone slightly after having a night to think it over.
"Last night everyone could truly see the passion I have for my job. Now that I have had time to gain my composure, I can see that while I don't agree with the unfair line call, in the heat of battle I let my passion and emotion get the better of me and as a result handled the situation poorly," the American said.
"I would like to thank my fans and supporters for understanding that I am human and I look forward to continuing the journey, both professionally and personally, with you all as I move forward and grow from this experience."