The newborn royal will be called His Royal Highness Prince Louis of Cambridge.

Britain’s Duke and Duchess of Cambridge have named their third child Louis Arthur Charles, a choice that confounded expectations.

His Royal Highness Prince Louis of Cambridge, as he will be called, is fifth in line to the British throne, after grandfather Prince Charles, father Prince William and his two older siblings.

More than 100,000 bets were placed across the United Kingdom betting industry on the baby name, with both Albert and Arthur leading the way as the bookmakers’ favourite.

But William and Kate have plumped for a name used for centuries across the Channel by the French, who have had 18 kings called Louis.

William and Kate’s third child was born on Monday and weighed eight pounds and seven ounces (3.8 kilogram).

Louis is a younger brother to Prince George, 4, and Princess Charlotte, 2, and is Queen Elizabeth II's sixth great-grandchild.

His birth was also a significant moment for Charlotte, the first princess who will not be overtaken in the line of succession by her younger brother.