Harry and Meghan have broken with royal convention by making a personal decision not to use a title for their baby boy. He will simply be known as Master Archie Mountbatten-Windsor.

As the first born son of a duke, Archie could have become Earl of Dumbarton (one of Harry's subsidiary titles) or have been Lord Archie Mountbatten-Windsor.

A source said: "They have chosen not to use a courtesy title."

The decision fits in with Harry and Meghan's desire to give their son as normal a life as possible despite his royal heritage.

Harry, who has admitted he once "wanted out" of the royal family, has spoken in the past of how he was always more comfortable being Captain Wales in the Army than being Prince Harry.

Archie means "genuine", "bold" and "brave", and is German in origin. Short for Archibald, it is now given as a name in its own right.

Harrison means "son of Harry" so is likely to be a tribute to the duke. It is English in origin and famous Harrisons include the Star Wars actor Harrison Ford.

Archie is not entitled to be an HRH or a prince because of rules set out more than 100 years ago by George V.

The couple's Instagram account announced: "The Duke and Duchess of Sussex are pleased to announce they have named their first born child: Archie Harrison Mountbatten-Windsor

"This afternoon Their Royal Highnesses introduced Her Majesty The Queen to her eighth great-grandchild at Windsor Castle. The Duke of Edinburgh and The Duchess' mother were also present for this special occasion."

The family of three were pictured in a black and white snap showing off baby Archie to the Queen and Philip, alongside Meghan's mother Doria Ragland.

Harry and Meghan's first born, who is seventh in line to the throne, made his world debut with his besotted parents at Windsor Castle on Wednesday.

Proud mother Meghan described him as having the "sweetest temperament" while a delighted Harry called him "our own little bundle of joy".

The duchess added: "It's magic, it's pretty amazing. I have the two best guys in the world so I'm really happy."

As her husband held their son, Meghan added: "He has the sweetest temperament, he's really calm."

As they both laughed, Harry said: "I don't know who he gets that from."

Meghan added: "He's just been the dream so it's been a special couple of days."

Amid surroundings steeped in royal history, the latest royal baby made his debut behind closed doors, with a small press pool of only one reporter, one photographer, three cameramen, as well as the couple's own private photographer and a household press officer photographer.

Asked who the baby takes after, Meghan said: "We're still trying to figure that out."

Harry said: "Everyone says that babies change so much over two weeks. We're basically monitoring how the changing process happens over this next month really. But his looks are changing every single day, so who knows."

Baby Sussex was sleeping soundly, wrapped in a white blanket and wearing a delicate white knitted hat.

Asked how he was finding parenting, Harry said: "It's great. Parenting is amazing.

"It's only been two-and-a-half days, three days, but we're just so thrilled to have our own little bundle of joy."

Harry said they were looking forward to spending some "precious times with him as he slowly, slowly starts to grow up."

As is the custom for royal babies, Harry and Meghan will have shared news of their choice with the monarch before releasing it to the public.

The duke and duchess's son arrived overdue on May 6 at 5.26am, weighing 7lb 3oz (3.26kg).

Among the bookmakers' favourites were Alexander, Arthur, Albert, as well as James and Philip while Spencer was a late favourite, but Archie was a surprise choice.

Archie is an increasingly popular name in Britain and was among top 20 most common boy's names in 2017, according to the Office for National Statistics.

Mountbatten-Windsor is a surname used by some members of the royal family.

AAP