The baby girl was born at 11.40am on Friday at Santa Barbara Cottage Hospital in California weighing 7lb 11oz.
Meghan and Harry described their bundle of joy as “more than we could have ever imagined”, as they enjoy this “very special time” with two-year-old son Archie, who is now a big brother.
Their name choices pay tribute to both the duke’s mother – the late Princess of Wales – and the Queen – “Lilibet” has been her family nickname since she struggled to pronounce her own name “Elizabeth” as a young child.
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The monarch, Prince Charles and Camila, and the Duke and Duchess of Cambridge’s social media accounts have all shared their congratulations.
Here’s how Twitter has responded to the news and, more specifically, to the couple’s decision to call her Lili Diana:
Sussex Family of 4!
Lilibet "Lili" Diana
Sister to Archie Harrison
Daughter to #HarryandMeghan
May she be as… https://t.co/EzmW2MOzGK
The Sussexes’ press secretary confirmed the baby had been named Lilibet “Lili” Diana Mountbatten-Windsor.
She added: “Both mother and child are healthy and well, and settling in at home.
“Lili is named after her great-grandmother, Her Majesty the Queen, whose family nickname is Lilibet.
“Her middle name, Diana, was chosen to honour her beloved late grandmother, the Princess of Wales.”
Harry had long been expected to honour his late mother who died in a car crash when he was 12.
The couple’s spokeswoman added: “The duke and duchess thank you for your warm wishes and prayers as they enjoy this special time as a family.”
Harry and Meghan are now on parental leave, their website said.
Prince Charles and Diana following the birth of their second son Harry in 1984PA
They asked well-wishers to support organisations helping women – Girls Inc, Harvest Home, CAMFED or Myna Mahila Foundation – rather than send gifts.
The new baby is the Queen’s 11th great-grandchild, and the first to be born since Philip’s death.
But with the Sussexes living in California and amid troubled relationships with Harry’s family, it is not known when or if the new addition will meet the Queen and the rest of the royals.
The duke has accused his family of “total neglect” when Meghan was feeling suicidal amid harassment on social media.
In his Apple TV mental health series, he lambasted the parenting skills of the Prince of Wales, criticising his father for expecting his sons to endure the pressures of royal life, just as Charles has done, instead of protecting them.
Just like Archie was not entitled to be a prince or an HRH when he was born in 2018, the Sussexes’ daughter is not permitted to be a princess or an HRH due to rules set down more than 100 years ago by George V.
Meghan controversially claimed during the Oprah broadcast that Archie had his right to be a prince taken away from him because of his race.
In fact, he was too far removed from the crown because although he is a great-grandchild of a sovereign, he is not the “eldest living son of the eldest son of the Prince of Wales”, as George V’s rules required.
Lili will be entitled to be a princess and Archie a prince, both with HRH styles, after the death of the Queen and when Charles becomes king.
This is because they will have moved up the line of succession to become the children of a son of a monarch.
Despite Harry and Meghan quitting as senior working royals, the baby still has a place in the line of succession.
She is eighth in line to the throne, coming after Archie, who is seventh, and before the Duke of York, who has dropped to ninth.
The new baby is also a first cousin of Prince George, Princess Charlotte and Prince Louis and a fifth grandchild for Charles, but will grow up across the Atlantic, thousands of miles away from the royal family.
Lili is the most senior royal in the line of succession to be born overseas and would be eligible to become president of the United States.