The suit was filed Wednesday in a Hawaii federal court, the same day the Los Angeles Times published an article in which six women, including actresses Olivia Munn and Natasha Henstridge, accused Ratner of allegations ranging from sexual harassment to assault.
Ratner denied the allegations outlined in the report to CNN through his attorney, Martin Singer.
"Brett Ratner vehemently denies the outrageous derogatory allegations that have been reported about him, and we are confident that his name will be cleared once the current media frenzy dies down and people can objectively evaluate the nature of these claims," the statement read. "He understands the seriousness of this issue and the importance of addressing the concerns of victims of sexual misconduct both in the entertainment industry and beyond."
In his suit, Ratner accuses Hawaii resident Melanie Kohler of defaming him with a post on her Facebook page.
Kohler's name was not included in the Los Angeles Times story. According to Ratner's suit, Kohler's Facebook post appeared a week before the story's publication.
"Commencing on or about October 20, 2017, Defendant recklessly and/or intentionally posted a statement on her Facebook page claiming that "Brett Ratner raped [her];" Ratner "was a rapist on at least one night in Hollywood about 12 years ago;" and Ratner "preyed on me as a drunk girl [and] forced himself upon me," the suit states.
Ratner contends that Kohler's allegation "is entirely false, fabricated, and fictional" and that she made the posting with the intent to harm his reputation and professional standing.
The director is claiming that the allegations have hurt his career and caused him "emotional distress, worry, anger, and anxiety."
Bill Burton of public relations firm SKDnickerbocker is acting as spokesman for Kohler.
"The goal of these lawsuits is to intimidate women," Burton said in a statement to CNN.
"Our goal is to stop the behavior," Burton added. "Melanie will not be intimidated."
"Mr. Ratner and his lawyers can try to erase the truth through threats and intimidation, but courts decide cases based on the facts and the law," Kohler's attorney, Robbie Kaplan said in a statement. "Our message to Mr. Ratner and his lawyer is short and simple: See you in court."
Ratner is seeking an unspecified amount of damages as well as reimbursement of legal fees. He is requesting a jury trial.