Could Cameron Diaz be the next Mrs. Benji Madden?

Strolling hand-in-hand along the cobbled streets of Positano, on Italy’s Amalfi Coast, Cameron Diaz and Benji Madden turned every head they passed last month. But it wasn’t just the star-wattage that had locals coughing into their cappuccinos — the unlikely couple’s predilection for PDA also caused ripples along the Italian coast.

“Going on appearances alone, people can’t help but stare, as they look completely mismatched,” a friend of the actress admits to The Post.

Indeed, the heavily inked 35-year-old rocker, whose romantic history includes Paris Hilton and Holly Madison, couldn’t be further from the 41-year-old actress’ usual type — which the friend describes as “clean-cut but with a bad-boy edge.”

Nonetheless, Diaz’s pals say that she might be willing to relinquish her status as one of Tinseltown’s most committed bachelorettes. The actress — who, in a recent interview, stated, “I don’t know if anyone is really naturally monogamous” — is seriously considering a walk up the aisle.

“Benji has pretty much moved into her house in Beverly Hills, and they’ve talked marriage,” her friend reveals. “None of us would be surprised if she called us and said: ‘Guess what? I’m Mrs. Madden!’ ”

So how in the world did one of Hollywood’s most beautiful women end up with … this guy?

It all goes back to 1995 and the surf-loving siren’s first high-profile relationship, with Matt Dillon, her co-star in “There’s Something About Mary.” A film industry insider says that Cameron was “besotted” with her beau, but their relationship unraveled after three years when Matt insisted that he wasn’t ready to settle down.

Oscar-winner Jared Leto helped to mend Diaz’s broken heart, but after a four-year affair, the pair parted ways in 2003. “Jared was pulling away from Hollywood and getting really into his band, whereas Diaz’s acting career was just reaching its peak,” another friend of the actress says.

Diaz thought she had found “The One” in Justin Timberlake. “They had incredible chemistry,” another associate confides. Despite Diaz’s insistence that she was the commitmentphobe in the relationship, sources say that the nine-year age gap proved to be insurmountable.

They called it a day in 2007, just months before Diaz was linked to Bradley Cooper — who was still married to Jennifer Esposito at the time. The A-listers attended a New York Giants game together and were spotted arm-in-arm in Central Park, but Cooper’s rep insisted reports of a romance were “not true.”

Diaz’s predilection for “Mr. Wrong” showed no sign of abating in 2008 when she hooked up with British model Paul Sculfor, a former construction worker who had previously dated Jennifer Aniston. “He was basically a bit of arm candy for her,” a friend reveals. After just 11 months, the pair went their separate ways, and friends say Diaz started to give up on the idea of her one true love. “All the failed romances made her pretty cynical,” a friend tells The Post. “It was around this time that she started saying that she didn’t believe in marriage.”

Adam Levine and Keanu Reeves are rumored to be among the scored-out names in Diaz’s little black book, but it was a very public relationship with Alex Rodriguez that managed to raise even Hollywood’s most heavilly Botoxed brows.

In 2010, the Yankees slugger — whose exes include Madonna and Kate Hudson — added another notch to his bedpost after homing in on Diaz at a Super Bowl party.

The actress was “infatuated” with A-Rod, a Rodriguez source tells The Post. “She met his kids and moved to Miami to be near him.”

Despite Diaz’s attempts to ingratiate herself to the playboy — she was pictured feeding him popcorn — she was left “devastated” when A-Rod ended the relationship in 2011.

It was that ill-fated coupling that made the “Sex Tape” star rethink her “type” altogether. In May of this year, her longtime friend Nicole Richie, wife of Benji’s brother and bandmate Joel, played Cupid.

“Nicole told Cameron that she needed to cut the douchebags loose. She assured her that Benji was the loveliest guy, with talent but no ego,” the insider reveals.

It seems Richie’s instincts were spot-on. Friends insist that the couple share “a ton” of common interests. “They are both fitness fanatics and enjoy the same food, bad jokes and even a lot of the same music,” a Madden pal reveals. “Benji thinks she’s the coolest chick he’s ever met, and he can’t believe his luck that she’s into him, too.”

Gossip blogger Perez Hilton thinks Diaz has decided to broaden her dating horizons as she’s entered her 40s.

“With age comes wisdom and a more adventurous palate,” he tells The Post. “I used to hate olives but now I love them. Benji Madden is Cameron Diaz’s olive!”