American player Sloane Stephens says she received more than 2,000 messages of abuse - including racist and sexist comments - after losing to Germany's Angelique Kerber in the US Open.
Stephens, who won the 2017 title in New York, posted examples of the abuse in an Instagram story on Saturday.
"I am human. It's so hard to read messages like these," she said.
"This type of hate is so exhausting and never ending. This isn't talked about enough, but it really sucks."
Stephens, 28, lost 5-7 6-2 6-3 to 2016 champion Kerber on Friday.
"After last night's match I got 2,000-plus messages of abuse/anger from people upset by the results," added the former world number three, who is now ranked 66th.
Campaigners - including the Centre for Countering Digital Hate, an international organisation which operates from the US and the UK - have called for permanent social media bans for anyone posting racist abuse.
In July, UK prime minister Boris Johnson met with social media executives to discuss the online racism aimed at England footballers, as well as asking how their companies are tackling bullying.
Last month Instagram announced new features designed to restrict abusive messages during "sudden spikes".
It attempts to stop abuse from large numbers of people "who simply pile on in the moment", the company said.