Hollywood- JACK Nicholson is denying a shocking claim that he may be the father of an illegitimate handicapped son and has attempted to keep it a secret.

In “Five Easy Decades,” an unauthorized biography out this October from Wiley, author Dennis McDougal says the Oscar-winning wild man is known “by most counts” to have one legitimate daughter and five love children.

But, the book claims, “There are two other possibles whom those closest to Jack whisper about, including one young man who lives with handicaps brought on by his actress mother’s drug abuse . . . These are among the closely held secrets he has generally succeeded in keeping from his fans.” He doesn’t identify either.

Nicholson’s lawyer, Abe Somer, told Page Six: “The allegations of the handicapped son are false and inaccurate. There is no handicapped son of Mr. Nicholson.” He declined to comment on McDougal’s allegation of a second unknown love child, adding, “Let’s respect his privacy.” Somer also said Nicholson has four, not five, illegitimate kids.

McDougal told us his information about the alleged disabled son “comes from a very good source, but she . . . would not let me use her name.”

The 70-year-old star’s first child, Jennifer, was the product of his six-year marriage to actress Sandra Knight. He then had Love Child No. 1, a son named Caleb born in 1970 after a fling with his “Five Easy Pieces” co-star Susan Anspach.

The boy was legally adopted by “Lost in Space” star Mark Goddard, who married Anspach four years later.

Nicholson has also sired a daughter with a former Monkey Bar waitress, Jennine Gourin, and bought her silence with a settlement “rumored to be in the mid-six-figures,” the biographer claims. Nicholson’s most publicly known love kids are Lorraine, 16, and Raymond, 15, by his ex-girlfriend, actress Rebecca Broussard.

The actor’s penchant for sleeping with lots of women is well known. “I’m interested in sex. I’m preoccupied with sex. I love it,” he once gushed, according to the book. He also panned condoms, saying using them was like wearing a “warm garbage bag.”