Gayle (25) gave birth to a little baby boy at 4.14am yesterday.
Baby Brandon weighed in at 9lb 13 ounces.
A spokesman for Dundalk band The Corrs said both mother and baby were doing well.
The couple have been dating for a year and a half and became engaged last winter.
A message on the band's official website said everyone was "absolutely thrilled" at the news.
Last month fiddle player Sharon Corr, who lives in Belfast with her husband Gavin Bonnar, gave birth to their first child, also a boy.
The Corrs' drummer Caroline already has two children.