Prince William and Kate Middleton officially announced the name of their newborn son, now third in line to the throne, Wednesday.

The royal baby's name is George Alexander Louis.

His Royal Highness Prince George of Cambridge. (Photo:AFP)

Kensington Palace's statement read: “The Duke and Duchess of Cambridge are delighted to announce that they have named their son George Alexander Louis. The baby will be known as His Royal Highness Prince George of Cambridge.”

According to the British Monarchy official website, before 1917, members of the British Royal Family had no surname, but only the name of the house or dynasty to which they belonged.

For the most part, members of the Royal Family who are entitled to the style and dignity of HRH Prince or Princess do not need a surname. So a surname is not necessarily be required for Prince George of Cambridge.

However, if the Duke and Duchess of Cambridge want to include a surname for Prince George, there are three choices available - Mountbatten-Windsor, Wales or Cambridge.

In 1917 George V adopted Windsor - after the castle of the same name - as the "surname" of his family.

And then in 1960, The Queen and The Duke of Edinburgh combined their surnames to make Mountbatten-Windsor - their direct descendants can use this name but it isn't binding.

The official last name of Prince William is Mountbatten-Windsor. His full name is William Arthur Philip Louis. In his military role, he used Wales, which is taken from his father, as his surname. Similarly Cambridge, the title given to William and Kate when they married, could be used for Prince George.

Unless The Prince of Wales chooses to alter the present decisions when he becomes king, he will continue to be of the House of Windsor and his grandchildren will use the surname Mountbatten-Windsor.

On Tuesday, Kate Middleton and Prince William introduced the royal baby on the steps of St. Mary’s Hospital in London. William told reporters, "We are still working on a name, so we will have that as soon as we can" and "It is the first time we have seen him really, so we are having a proper chance to catch up."

The announcement from Prince William and Kate -- just two days after the baby's birth -- was quick, by royal standards.

Queen Elizabeth II and the Duke of Edinburgh took a month before settling on the name Charles for the Prince of Wales. Prince Charles and Princess Diana took a week before settling on William's names.

Earlier Wednesday, Queen Elizabeth II visited with her new great-grandson at Kensington Palace for the first time, before William and Kate took the royal baby to visit his maternal grandparents in Bucklebury, a village west of London.