Hollywood stepped up Monday to defend Serena Williams.

The tennis superstar found herself in the middle of controversy after this weekend's US Open final.

Williams lost to Japan's Naomi Osaka and was sanctioned fines totaling $17,000 for three violations after a heated exchange with umpire Carlos Ramos.

Serena Williams is fined $17,000 for violations during her US Open loss

Ramos had issued the violations against Williams after she accused him of being unfair during Saturday's match.

The 23-time Grand Slam champion has faced racist attacks for most of her career, and after the match Saturday, said she believes sexism is rampant in the tennis world.

Serena Williams is calling out sexism in tennis. Here's why.

"Harry Potter" author JK Rowling defended Williams after cartoonist Mark Knight released an editorial cartoon which featured an irate Williams jumping on her tennis racquet.

"Well done on reducing one of the greatest sportswomen alive to racist and sexist tropes and turning a second great sportswoman into a faceless prop," Rowling tweeted along with Knight's tweet of his drawing.

Actress Reagan Gomez also tweeted about the cartoon, writing "It's not just about sexism."

"The other player (not Naomi???) isn't drawn the way Serena is," Gomez wrote. "You know why. Anyone who tells you this isn't misogynoir is gaslighting you. Don't allow them to."

Several celebs took to social media over the weekend to support both Williams and Osaka.

"All praise to both [queens] @serenawilliams the best athlete the world has ever seen & @Naomi_Osaka_ demonstrating #BlackGirlMagic & fierce determination," actress Gabrielle Union tweeted. "Very proud. Tears watching the hug."

The International Tennis Federation released this statement Monday:

"Carlos Ramos is one of the most experienced and respected umpires in tennis. Mr. Ramos' decisions were in accordance with the relevant rules and were re-affirmed by the US Open's decision to fine Serena Williams for the three offenses.

"It is understandable that this high profile and regrettable incident should provoke debate. At the same time, it is important to remember that Mr. Ramos undertook his duties as an official according to the relevant rule book and acted at all times with professionalism and integrity."