WWW- Paris Hilton is a singer, actress, accidental porn star – and, we now learn, a bit of a Mafia princess.

The hotel heiress’ parents almost didn’t get married because her maternal grandmother was married to a mobster, a new book reveals.

Jerry Oppenheimer reports in “House of Hilton” that Kathy Richards – known as “Big Kathy” -was hitched to a notorious gangland figure when her daughter, “Little Kathy,” fell in love with Paris’ dad, Rick Hilton.

Oppenheimer, whose Crown book comes out in November, is withholding the mob guy’s name for now. But he reports that federal prosecutors linked him to Mafia families in New York, Philadelphia, Detroit and Chicago.

“Big Kathy used to boast to friends … that ‘if you ever need someone taken care of,’ her husband had the muscle to handle it.”

But Big Kathy got nervous when her daughter hooked up with Rick. “I can’t have the Hiltons finding out what [my husband] does,” she told a friend.

Big Kathy promptly divorced the potential wedding-spoiler, one of four husbands she collected. The gentleman later died of a heart attack – just before he was due to serve 15 years for counterfeiting, money-laundering and other charges.

Even so, Mama Richards was banned from the Hilton estate in Los Angeles unless the family patriarch, Barron Hilton, was out of town, according to Oppenheimer. “Barron couldn’t stand being around Kathy’s mother,” a source told Oppenheimer. “He used to call her ‘The Madam’ – as in bawdy house madam.”

Word is her mobster gave Big Kathy the same big honking diamond ring that he’d given earlier molls. “He’d always get it back from them,” a source tells us. “But he never got it back from Big Kathy.”

A spokesman for the Hiltons, who are said to be dreading the book, declined to comment. But Paris still cherishes the memory of her grandma, who died in 2002 at the age of 63.

“We were, like, best friends,” Paris says in September’s issue of Blender. “She would say, ‘You’re my Marilyn Monroe. You’re my Grace Kelly. You’re going to be the most famous woman in the world.’ … I feel like she made all this happen.”