The Take That star's wife, Dawn, went into labour but the baby girl did not survive, reported Daily Mail online.
Barlow released a statement after the heartbreaking news, saying, "Poppy Barlow was delivered stillborn on August 4th in London. Our focus now is giving her a beautiful funeral and loving our three children with all our hearts. We'd ask at this painful time that our privacy be respected."
He took to Twitter to let fans know he has been touched by their messages.
"Your kind words and lovely messages are overwhelming. Thank you," he posted.
The star's fans have rallied around the singer since the news broke, setting up a donation page on a charity website, which aims to raise 100,000 pounds for stillbirth and neonatal death charity Sands in memory of Poppy.