Looks like Hugh Hefner has a new Number One girl: Anna Sophia Berglund.

While Anna has been named as the gal keeping Hef company since Crystal Harris left him days before their wedding, last night they made their public debut together.

Hugh, 85, and Anna, 25, were seen sitting next to each other all night at the annual Kandyland event at the Playboy Mansion on Saturday ... where Hefner wore his standard robe and Anna wore some sexy cheetah print lingerie.

The two were seen leaving the party together too.

And it sounds like Anna isn't the only one Hef's seeing these days, as he tweeted yesterday "I haven't been in a one-on-one relationship since the end of my marriage in 1998."

In another tweet he responded to "rumors" he's also dating Shera Bechard, saying "It's more than a rumor."

It wasn't just Hugh and Playmates at the party last night though -- celebs like Paris Hilton, Alex Pettyfer, Amber Rose and Corey Feldman were also in attendance. Check out all the photos above!

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