The Duke and Duchess of Cambridge have called their new baby Louis Arthur Charles.
William and Kate's third child - who is fifth in line to the throne - was born on Monday.
He weighed 8 pounds 7 ounces.
The Duke and Duchess of Cambridge are delighted to announce that they have named their son Louis Arthur Charles.
The baby will be known as His Royal Highness Prince Louis of Cambridge. pic.twitter.com/4DUwsLv5JQ
— Kensington Palace (@KensingtonRoyal) April 27, 2018
He's a little brother for Prince George and Princess Charlotte.