Rory didn’t unveil his baby’s face, but shared an adorable black and white picture of him holding onto his newborn’s hand.
He wrote: “Poppy Kennedy McIlroy, born August 31st, 12:15pm.
“She is the absolute love of our lives. Mother and baby are doing great.
“Massive thank you to all the staff at Jupiter Medical Center and Dr Sasha Melendy for their amazing care.”
“I was waiting for that phone call last week and it didn’t come, and my caddie, Harry, has been keeping his phone in his pocket just to make sure, Nothing as of yet. But. If that call comes I’m out of here. Yeah, out of here.”
News of Rory’s wife pregnancy was confirmed during a broadcast of the third round of BMW Championship.
The Golf Channel’s Steve Sands told viewers Erica was due “anytime now”.
Rory and Erica tied the knot at Ashford Castle in Mayo in 2017.
They got engaged in 2015 while on holiday in Paris.
He previously gushed about his wife, who he said “brings such a level of normality to everything”.
The golfer said: “She has a calming presence, a sereneness and that’s not just on me; it is noticeable in any company.
“She never wants to be the centre of attention and is always very comfortable in the background,” he added to The Irish Independent.