It's a girl!

The Duchess of Cambridge Kate Middleton has given birth to a baby girl.

FILE: Catherine, Duchess of Cambridge, in west London on 12 March, 2015. Picture: AFP.

JOHANNESBURG - The Duchess of Cambridge Kate Middleton has given birth to a baby girl.

She was born at 08:34am and weighs 3.7kg.

The announcement was made outside Buckingham Palace.

The Duchess of Cambridge gave birth to her second child at the St Mary's Hospital in London.

Kate gave birth to her first child, Prince George Alexander Louis, in July 2013 at the same hospital to a worldwide media fanfare.

The baby will be fourth in line to the throne.

Her husband, Prince William, has reportedly taken paternity leave and is with her in the maternity ward.

Kensington Palace says both mom and baby are doing well.

William was born at the same hospital to the late Princess Diana in 1982.

Earlier, bookmakers were tipping the child to be a girl, with Alice, Elizabeth, Charlotte and Victoria the favourite names.

At the same time, the United Kingdom's Prime Minister David Cameron has wished the royal family well as they welcome their second child.

Kate, 33, and William, 32, met as students at St Andrews University in Scotland, married in a spectacular ceremony at Westminster Abbey in April 2011 and have since become global stars.

When Kate leaves hospital after giving birth, the couple will initially return to their London residence, Kensington Palace, for a couple of days, before heading to Anmer Hall, their country mansion on the queen's Sandringham estate in Norfolk, to the northeast of London.