The Grammys -- Stage Crasher ARRESTED After Run-In with Jennifer Lopez

The moron who crashed the stage at The Grammys -- only to get kicked off stage by Jennifer Lopez on live TV -- was arrested for trespassing directly following the awards show ... and it's not the dumbest stunt he's ever pulled.

The idiot who wound up in handcuffs is Vitalii Sediuk ... the same dumbass who got slapped in the face by Will Smith last year (and rightfully so) when he tried to surprise the actor with a kiss on the lips on a red carpet.

During the Grammys, Sediuk somehow weaseled his way backstage ... and when Adele was announced as the winner for Best Pop Solo Performance ... Vitalii rushed to the podium and tried to grab the mic from presenter Jennifer Lopez.

Sediuk managed to get out a few words ... saying, "Thank you, Adele. You’re my inspiration” ... but Lopez quickly ripped the mic back and shooed him offstage.

Directly following the show, cops arrested Sediuk for trespassing -- and he spent the night in a jail cell ... this according to the Hollywood Reporter.

Sediuk told THR he's just a prankster and meant no harm -- adding, "I’m not a crazy guy. I just think differently."