We've always known that PRINCE HARRY can have a good time.  And he proved that he's still on his game by PARTYING NAKED in Las Vegas over the weekend.

It happened Friday night when Harry and some friends went down to the bar in their hotel looking for chicks.  They found some, and pretty soon, everybody was in Harry's VIP suite playing STRIP BILLIARDS.

And someone was kind enough to snap some photos.  Two of them ended up online yesterday.

One pic shows a FULL-FRONTAL Harry . . . although he's cupping his royal package so you can't see it.  And there's a girl who's at the very least TOPLESS snuggling up to him from behind.

In the second photo, it's Harry who's coming up on a girl from behind.  They're both naked . . . and Harry's ROYAL CRACK is exposed.

A spokesman for the royal family says, quote, "We have no comment to make on the photos at this time."

Pics are posted at TMZ.