Jay Z may be the next Ed McMahon ... 'cause his search for new rap stars continued last night in Chicago during a concert -- and this time he chose a girl looking for a second chance.
HOVA brought the girl on stage at the United Center after he spotted her holding a sign saying, "When I was 16 I rapped on this stage with you. I'm 19 now and I'm ready."
The girl -- named Monique -- laid down a track about her own life ... clearly impressing Mr. Carter in the process.
Monique then proved she's got some serious cojones ... and Jay's reaction is priceless.