Sean Penn, Charlize Theron are dating — but about his 67 guns ...

OK, the big news out of Piers Morgan’s “My Life and Other Celebrities� column for the Daily Mail is that Sean Penn and Charlize Theron really are dating — a detail Penn confirmed to the CNN host at his Haiti fundraiser, held the night before the Golden Globes.

As the event wrapped up in the wee hours of the morning, Piers revealed in the column, he’d wished Penn, “Congrats on a great night. And congrats on Charlize too.�

Penn, 53, laughed, Morgan said, then told him: “She’s a keeper, that’s for sure. … Well, I’ll do my best to keep her anyway!�

So let’s call that the final confirmation that they’re a couple, after People reported they had their hands “all over each other� at the event, and that they rang in the new year together at Penn’s place in Oahu, taking the same flight home and the next day reportedly leaving the 38-year-old actress’ home in separate cars.

But the other thing Morgan, an outspoken anti-gun advocate, mentioned in his column was this: His pal Penn owns 67 guns, a fact the actor admitted over the phone the day before the charity gala.

Penn was, however, “decommissioning,� he told the host.

“I’m melting down all the guns, and the ton of ammo I have, too, and the great artist Jeff Koons has agreed to make a sculpture out of it all to sell at my Haiti fund-raiser tomorrow night,� Penn told Morgan.

Ted Nugent would not approve.

The high bidder for the post-2nd Amendment work of art, which Penn introduced by saying he’d been influenced to purge his stockpile by Theron and Morgan? It was CNN’s silver fox Anderson Cooper, who at $1.4 million outbid Morgan while being egged on by Gwyneth Paltrow, Morgan said.

Cooper edged out Morgan himself, who’d also been gunning for the prize.

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