"I am truly perplexed to learn this editor of the Australian newspaper behind the blatantly racist & misogynistic cartoon of my wife is a 'Male Champion of Change" ... Is this supposed to be satire, too?"
Ohanian also alerts Australian Sex Discrimination Commissioner Elizabeth Broderick to the tweet by tagging her twitter handle.
Knight drew a caricature of Williams throwing a temper tantrum, which was printed in the Herald Sun, following her loss to Japan's Naomi Osaka in the US Open women's singles final in New York last weekend.
The illustrator said it was prompted by her "poor behaviour" shown during the match.
Williams, who was vying to equal Australian player Margaret Court's record of 24 grand slam singles titles, lost in straight sets after a heated clash with chair umpire Carlos Ramos over code violations that resulted in her being penalised a game.
But critics, most notably online, labelled the cartoon racist because it depicted Williams with big fat lips and masculine features.
Both Knight and Herald Sun editor Damon Johnston denied the image was racist, and in defiance, the Herald Sun reprinted the controversial cartoon on its front page alongside other caricatures of US President Donald Trump and North Korean leader Kim Jong-un.
"If the self-appointed censors of Mark Knight get their way on his Serena Williams cartoon, our new politically correct life will be very dull indeed," the paper wrote in an editorial on its front page.
Herald Sun editor Johnston had also defended the cartoon on Twitter.
"It rightly mocks poor behaviour by a tennis legend," Johnston tweeted.
SBS News has contacted the Herald Sun, a News Corp newspaper, for a response to Ohanian's comments.
Williams, 36, received a game penalty after she lashed out at chair umpire Carlos Ramos, calling him a "thief", after previous code violations for coaching and then smashing her racquet.
She insisted male players had called chair umpires much worse and she was being treated differently because she is a woman.
Williams was fined $17,000 for her three code violations during the US Open final against Osaka and again said after the match male players were held to a lower standard for court conduct.
“I’m here fighting for women’s rights and women’s equality,” Williams said at a news conference after the match.