Hayden Panettiere Says Oscar Winner Showed Her His Testicles at a Party

Hayden Panettiere says an Oscar-winning actor and director showed her his testicles, without consent, when she was just a teenager.

The actress has opened up about a ton of stomach-churning stories in her new memoir "This Is Me: A Reckoning" about the abuse she suffered while coming of age in Hollywood ... and she's now relaying a tale about a party she attended when she was 19.

Panettiere says she was leaving a gathering -- having grown uncomfortable while chatting with a group of men near the end of the night -- when a "well-respected" Oscar winner approached her as she was putting on a coat and complained about the gum stuck to his pants.

HP writes she looked down ... but, instead of gum, she found herself staring at the star's sack -- a sight at which she instantly recoiled.

Panettiere calls the moment a "head-scratcher" ... adding, "It hadn’t hurt me and I was sure it was a drunken joke, but I’d never seen a grown man do something like that. I was shocked.”

She says she didn't tell any of her friends at the time because "the moment had passed" and she just felt some people had grown up without learning proper manners.

'This Is Me' is full of harrowing stories ... from Hayden being essentially pushed into bed with a naked man on a yacht when she was 18 to her recollections of nearly dying during childbirth.