Her parents Prince Harry and Meghan Markle hold royal titles as do her older cousins Prince George, Princess Charlotte and Prince Louis.
But for the Sussex's youngest child Lilibet - she does not have a title or HRH status and is simply known as Lilibet Diana Mountbatten-Windsor.
However, this could all change in the future and she could become a princess with an HRH style - and it's down to a rule set down more than 100 years ago.
But will only happen when his grandfather Prince Charles becomes King.
The tradition stems from Harry's great-great-grandfather, George V when he issued a Letters Patent in 1917.
A spokesperson for Debrett’s previously told the Mirror: “In 1917, King George V ordered that only the grandchildren of the monarch would be entitled to use the style of prince or princess and HRH, the only exception to this order was that the eldest son of the eldest son of the Prince of Wales would also be entitled to use the style HRH and Prince."
This means that only Prince George - as a great-grandson of the monarch down the direct line of succession to the throne - was originally entitled to be a prince. He is the eldest son of the eldest son of the Prince of Wales.
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The Queen stepped in ahead of George's birth to issue a Letters Patent to ensure that George's siblings would have fitting titles.
However, this does not extend to Lilibet or her older brother Archie - although when Charles is King they will be the grandchildren of the monarch and can be styled HRH and prince or princess.
When Lilibet was born last June, she became eighth in line to the throne - and is the highest person in the line of succession to be born outside of the UK.
Mum Meghan gave birth to her in Santa Barbara and her and dad Harry have yet to bring her to the UK.
This means she has not met her grandfather Charles or great-grandmother the Queen in person.
There are hopes that Harry, Meghan, Archie and Lilibet could come to the UK later this year to take part in the Queen's Platinum Jubilee celebrations in June.
The bumper bank holiday weekend also coincides with Lilibet's first birthday on Saturday, June 4.
However, earlier this year, Harry released a statement saying he is unable to bring wife and their two children to the UK due to a lack of security.
He is said to be keen to bring Archie and Lilibet to visit his homeland but claims he is unable to do so as Harry and Meghan lost their taxpayer-funded police protection when they stood down as working royals.
The 37-year-old has applied for a judicial review of a decision not to allow him to personally pay for police protection for himself and his family when they are in the UK
Harry was told he would no longer be given the same degree of personal protective security when visiting from the US - despite offering to pay for it himself.
