The singer, 41, responded through a representative after actress Rose, 40, made a series of posts on Threads on Sunday alleging an incident at a Melbourne nightclub when she was in her 20s.
Her claims were made in response to a post by Complex Music referencing Perry's reaction to Justin Bieber and his Coachella 2026 performance.
Rose said it had taken her "almost two decades" to speak publicly about the alleged incident.
She wrote: "Katy Perry sexual assaulted me at spice market nightclub in Melbourne. Who gives a shit what she thinks.
"Though I am so grateful to have made it long enough to find my voice, it just shows how much of an impact trauma and sexual assault takes. Thank you for seeing me."
In a statement to Page Six, Perry's representative said: "The allegations being circulated on social media by Ruby Rose about Katy Perry are not only categorically false, they are dangerous reckless lies.
"Ms. Rose has a well-documented history of making serious public allegations on social media against various individuals, claims that have repeatedly been denied by those named."
Rose provided further details of the alleged incident in additional posts on Threads.
She said: "(Katy) didn't kiss me. She saw me 'resting' on my best friend's lap to avoid her and bent down, pulled her underwear to the side and rubbed her disgusting vagina on my face until my eyes snapped open and I projectile vomited on her.
"After it I threw up on her, I told the story publicly but changed it to be a 'funny little drunk story' because I didn't know how else to handle it. Later she agreed to help me get my US visa. So I kept it a secret. But I DID tell yall she wasn't a good person."
In further posts, Rose said she planned to report her experiences.
"I imagine they are past their statute of limitations, but all the more reason to try," she said.
"I have a long list, it will probably take more out of me than I'm prepared for, but I will come back here to update others on the process, as soon as I am ready."
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