The latest addition to the Duke and Duchess of Cambridge's family will be called Prince Louis Arthur Charles.
He'll be known as His Royal Highness Prince Louis of Cambridge.
Speculation that the couple were going to call the baby Albert came after it was spotted that a web page for Prince Albert had been created on the official Royal website.
But all those who placed bets on the name being Albert will be disappointed today, as Kensington Palace tweeted that his name is Louis.
Alexander was also in the running, with a high number of bets being placed on that name too.
On Wednesday at the Anzac Day celebrations, Prince William remarked that Alexander was "a good name" after he was asked by the Australian High Commissioner to the UK Alexander Downer if he'd thought of using the name.