Her spokesman says Bunton and her boyfriend Jade Jones named their son Beau.
This is their first child.
Bunton, 31, will have four months to stay home with Beau until she and the other Spice Girls hit the road in December.
Bunton's bandmate, Melanie Brown, recently gave birth to a daughter that she named Angel. She's been battling with the child's father, Eddie Murphy, for child support.
Photos: Celebrity Baby News