Kate and William have named their new baby Louis Arthur Charles.
The royal couple's third child - who is fifth in line for the British throne - was born on Monday.
He weighed 8 pounds 7 ounces.
He's the little brother of Prince George and Princess Charlotte.
The newborn will be formally known as His Royal Highness Prince Louis of Cambridge.
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
