Jay Z -- Brings ANOTHER Fan On Stage ... For Rap Redemption

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.