Mel B Spice Girls On Royal Wedding Guest List... AND Performing!!!

The Spice Girls aren't just reuniting, they're becoming a wedding band! But erm, only for one very special couple!!

Mel B went on "The Real" Tuesday and had a very hard time keeping anything secret about the group's involvement with the Royal Wedding -- first disclosing that all 5 girls got the invite from Prince Harry and Meghan Markle ... then really spilling the beans.

Scary Spice kept getting pressed for more deets by the 'Real' ladies, and eventually seemed to confirm the Spice Girls will provide some wedding entertainment, as well.