I saw Jack Nicholson three-way at Playboy mansion

Pamela Anderson is baring all.

The “Baywatch” actress revealed that she once witnessed actor Jack Nicholson have a threesome at the Playboy mansion.

Anderson wrote in her forthcoming memoir, “Love, Pamela,” that she caught “The Shining” actor with “two beautiful women with him” in a bathroom at the mansion.

“They were all giggling and kissing up against the wall, sliding all over each other. I walked by to use the mirror, bending over the sink to fix my lip gloss,” the 55-year-old wrote in her book. “Trying not to look, but I couldn’t help myself and caught his eye in the reflection. I guess that got him to the finish line, because he made a funny noise, smiled and said, ‘Thanks, dear.’”

Anderson recalled the spectacle in an exclusive interview with Variety, which posted tidbits from her memoir.

“It was just complete freedom,” recalled Anderson. “It was full of artists, philanthropists, intellectuals, chivalry, beautiful women. It was really an experience.”

Anderson has been spilling much Hollywood tea amid her book release, having recently revealed that Tim Allen once flashed her while they were filming “Home Improvement” together.

“On the first day of filming, I walked out of my dressing room, and Tim was in the hallway in his robe. He opened his robe and flashed me quickly — completely naked underneath,” recalled Anderson.

“He said it was only fair, because he had seen me naked. Now we’re even. I laughed uncomfortably,” she said.

The former Playboy model made her magazine debut in 1968 turning her into a sex icon. Her status was further boosted when a sex tape of her and her ex-husband Tommy Lee was leaked.

“Love, Pamela” is set to hit bookshelves on January 31.