Kate Middleton and Prince William Announce Name of Royal Baby Boy

Kate Middleton and Prince William's third child has a name fit for a king ... Louis Arthur Charles!

The name of the new little royal was announced Friday by Kensington Palace, and he will be known as His Royal Highness Prince Louis of Cambridge. Not too shabby for a 4-day-old.

As we reported ... Kate gave birth to her baby Monday at St. Mary's Hospital in London. As is tradition, the Town Crier announced the birth from the steps of the Lindo Wing of the hospital.

The smart money was on the name Arthur, because royals are traditionally named after relatives and Arthur is commonly used in the royal family. Louis was among the top contenders but was by no means the favorite. It's one of his older bro Prince George's middle names, and also one of William's.

Fittingly, his little Highness -- now fifth in line to the throne -- has taken the name made most famous by The Kingsmen ... no relation.

Congrats! Big things to come for little Louis, we are sure.