The new Royal prince has been named Louis Arthur Charles.
The Duke and Duchess of Cambridge revealed the name this morning.
The new prince, who was born weighing 8lb 7oz at 11.01am on Monday, is the couple's third child and fifth-in-line to the throne.
He was shown to the world by the proud pair on the steps of the Lindo Wing at St Mary's Hospital in Paddington, west London, just hours after his birth on St George's Day.
Prince George, four, and Princess Charlotte, two, had earlier visited their new baby brother.