Sylvester Stallone claims that he was once sequestered in a psychiatric ward, where a fellow patient attempted to rip his groin off.

In his upcoming memoir, “The Steps,” out Sept. 29, Stallone recounted his traumatic childhood and teen years.

The “Rocky” star told the New York Times in a profile published Saturday that he attended a high school that would punish teenaged students who misbehaved by putting them in “a place called Park Lodge or the Snake Pit.”

“On the outside it looked like a big, old Tudor home from the ’20s, and then you walked inside and you entered the heart of insanity,” he recalled. “The smell, the filth, people running around naked, clawing, hands tied, drooling. This is what they thought would impress you never to break the rules again.”

Stallone said he was left there for two weeks and was attacked by a “guy named Jay Bird.”

“He was big, had no hair, always naked, rotten teeth,” the actor explained. “They called him Jay Bird because he was always naked as a jaybird. And I go into the bathroom on the way to the food mess hall, and he comes in and comes around me and he’s like ripping on my throat and he is going into my pants and grabbing my groin.”

Stallone alleged that two guards ran in and began “beating the crap out of him [Bird] with razor straps.”

When he returned to school, the “Rambo” star said the principal asked if he’d learned his lesson.

”I said: ‘I learned a lot more than that lesson. A much better lesson: You can’t break me,’” he shared. “So when I got to the city [New York] and everything that came after that, I always felt I was unbreakable in that way. My heart could be broken, like every human being, but I’m talking about will.”

The NYT reached out to Stallone’s high school and a spokesperson responded that, while they hadn’t read the book, they respected the star’s “right to tell his story his own way” and apologized “for any trauma he remembers experiencing.”

Stallone also reveals in the wide-ranging profile that his mother was not a nurturing figure and his father was unpredictable and violent.

He also admitted to abusing steroids and struggling with bulimia while preparing for 1982’s “Rocky III.”

“Then it became an obsession,” he said, referencing how he curated his body to fit the “Rambo” and “Rocky” franchises.