Here is the lowdown on the newest addition to the royal family and her parents.
Who is Zara Tindall?Zara Tindall, nee Phillips, is the Queen’s granddaughter and daughter of the Princess Royal.
The former royal rebel – who once had her tongue pierced as a teenager – is a champion equestrian rider who won a silver medal in the London 2012 Olympics with Team GB.
She is married to former England rugby player Mike Tindall.
They wed in Edinburgh in July 2011 after an eight-year relationship.
The couple already have a four-year-old daughter, Mia.
And the new baby?The Tindalls’ new daughter is the Queen and the Duke of Edinburgh’s seventh great-grandchild.
The Duke and Duchess of Cambridge’s youngest child Prince Louis, who was born in April, was the Queen’s sixth great-grandchild.
The baby’s sister Mia was pictured holding the Queen’s famous black handbag when the monarch posed for an Annie Leibovitz photograph with her great-grandchildren to mark her 90th birthday in 2016.
Will the baby follow in Mia’s footsteps?Mia is known for being a cheeky youngster with boundless energy, and is often spotted charging around with her cousins Savannah and Isla Phillips at equestrian events.
Where is the baby in the line of succession?Quite far down – 19th in line to the throne.
Will the baby have a royal title?No – they will not even be an HRH.
Why not?Mike Tindall has no title himself and Zara, born down the female line as the offspring of the daughter of a sovereign, is not entitled to be an HRH.
Zara’s father, Captain Mark Phillips, was believed to have been offered an earldom by the Queen when he married Princess Anne, but chose not to take it.
What kind of life will the baby have? The Tindalls are known for their down-to-earth approach to parenting and relaxed attitude to life.
Hands-on father Tindall is often seen cheering on Zara at horse trials while carrying Mia on his shoulders or playfully throwing his feisty daughter in the air.
Zara, 37, has spoken of how fortunate she was to have had a “slightly more normal” upbringing than the rest of her royal relatives.
“I’ve been very lucky. My parents didn’t give us titles, so we’ve been able to have a slightly more normal upbringing. As soon as you’ve got a title, it’s very difficult to shed it,” she said.
The new baby can expect to grow up immersed in the equestrian world and to learn to ride at an early age.
How is the baby related to Prince George, Princess Charlotte and Prince Louis?They are second cousins.
Zara and the Duke of Cambridge are cousins. Zara is also George’s godmother.
Tindall once revealed that George’s first meeting with Mia when she was a baby was “carnage”, with most of George’s food going on the table rather than in his mouth.