A Beyonce fan in Copenhagen apparently snoozed through the life lesson about keeping your hands to yourself. He boldly slapped the singer's butt while she was performing -- and got a rebuke from Queen Bey herself.

While Bey was performing 'Irreplaceable' last night (May 27) as part of her Mrs. Carter Show World Tour, looking snazzy in her sparkly sapphire pantsuit, she thrust the mic into the fan's face. He sang along, and the diva said, "Alright, boo boo."

Apparently, he felt enough of a kinship and a camaraderie at that moment to reach out and touch someone ... the "someone" being Bey's bodacious ass, which he playfully slapped as she walked past.

Bey was not amused and she threatened to have his ass tossed.

"I will have you escorted out right now ... alright?" she said sternly, with a slight laugh before belting out the rest of the song. She barely missed a butt -- er, beat.

Being verbally dressed down by Bey should remind the offender it's not polite to get all handsy with a stranger, let alone a superstar. At least he has a great story to share with friends and the unlucky chicks he tries to pick up at the bar: "I was almost thrown out of a Beyonce show for touching her butt!"

Such a gentleman.